Blunderbuss

Meaning: a gun; more detail here, if you're into that kind of thing.

Usefulness: 3

Logofascination: 2 (it's a perversion of donderbus, Dutch for thunder-gun, and the OED backs up Looper in suggesting that blunder comes into the name by way of "some allusion to its blind or random firing". A defining feature: "capable of doing execution within a limited range without exact aim." It's always nice when a scriptwriter has done their research.)

Chironomatic

Meaning: relating to chironomy, which is the art or science of what to do with your hands; John Bulwer also applied it to the Art of Manual Rhetoricke, which we much more boringly call sign language.

Usefulness: 1 (Can be applied to all those people who are happy to tell you what to do with your hands while presenting or, Google suggests, kissing. Also conductors - though it seems to have some kind of technical application to choirs - and Italians, which is how Rabelais uses it. Is a stereotype any more true because it is 400 years old?)

Logofascination: 2 (ah, humanity: concerns of chironomy bind actors, presenters, politicians, rhetoricians and, apparently, lovers, across time, space and YouTube.)

Data

Meaning: information, pieces of information

Usefulness: 2 (it's not very exciting, but we keep using it, so it must be useful.)

Logofascination: 1 (because, and only and wholly and solely because, Sir Thomas has the first citation for this word in the OED. He used it in 1645, forty-six years - yes, forty-six - before the next citation*. See graph below for evidence of how ahead of the curve Sir Thomas was on this one.  Some guy is cited under datum from 1630, in a text called Most Easie Way Finding Sunnes Amplitude, which is clearly an early example of spam.)

Metopomancy

Meaning: divination by looking at the face, particularly the lines and wrinkles on the forehead.

Usefulness: 1 ("My morning metopomancy grows grimmer by the day." "It doesn't take metopomancy to reveal that you're worried about something, my dear, particularly with those eyebrows.")

Logofascination: 1 (Rabelais, Urquhart, Cotgrave and Mrs Byrne have all used it; if that's not enough word cred for you, I don't know what is)

Eleemosynary

Meaning: charitable; related to charity, alms or alms-giving

Usefulness: 2 ('eleemosynary works' could be listed as an impressive hobby, or it could be used to obscure political arguments - see below.)

Logofascination: 1 (it's the double e, I think)

Nival

Meaning: snowy. Bonus synonym: niveous.

Usefulness: 3 (basically a straight synonym for snowy, with extra science points; could be handy in Scrabble)

Logofascination: 2 (possibly because I've never seen snow)

Auscultation

Meaning: Listening, hearkening; in particular, listening to someone's insides with a stethoscope.

Usefulness: 2 (An impressive way to describe listening to music, podcasts, gossip, or other things generally not considered Productive: "What have you been doing all afternoon?" "I did quite a bit of auscultation, actually."  n.b. may not be successful if used around doctors or nurses.)

Logofascination: 2

Firnification

Meaning: the process by which snow becomes a glacier; firn is old snow. It's from a German word meaning 'of last year', which has the rare honour of being described as a 'useful word' by the Online Etymology Dictionary.

Usefulness: 1 (Used symbolically - unless you happen to live on a mountain top - this is a ridiculously useful word for all those things you haven't done for far too long. "The only way to overcome the firnification of my ironing basket was to throw it out."  "The firnification of the editor's slush pile was complete: later generations would be able to chart publishing trends by measuring the layers of boy wizard, vampire and erotic fiction.")

Logofascination: 1 (there is something about words for very specific things, and f-words - fuliginous is quite popular, for some reason)

Pandect

Meaning: a book of everything! Used by the Romans to refer to books of the law, this word's Greek origins mean all-receiving (an inn-keeper was a pandocheus). It was apparently the title of a few works of 'universal knowledge', or as we might call them, encyclopedias.

Usefulness: 1 ("I refer you to the great pandect, Wikipedia..." "My satchel is weighed down by the latest tax pandects." "The company OHS pandect has been revised as a direct result of your behaviour at last week's dinner.")

Logofascination: 1 (Romans and Greeks and, yes, Sir Thomas)

Crenellated

Meaning: having crennelles (embrasures* - the notches in a castle's battlement); stretched poetically to describe anything notched, or even vaguely jagged (e.g. mountains, skylines). Only very slightly different to crenulated, a botanical term meaning notched or scalloped (i.e. the same thing, but of plants rather than castles).

Usefulness: 2 (depending on how often you visit castles, or require overly poetic terms for such things: "As you can see, the graph of last quarter's returns is unfortunately crenellated.")

Logofascination: 1 (possibly influenced by an overly romantic view of castle life)

Geomancy

Meaning: divination by interpreting or joining together dots and lines; either on the ground (possibly after throwing handfuls of dirt in the air) or on paper. That's right, Mr Squiggle and the eponymous Miss Jane were actually geomancers - they must have edited out the bit concluding each episode where they predicted the future.

Usefulness: 1 (can be applied to handwriting, art, a dirty bathroom etc.)

Logofascination: 2

Paronomasia

Meaning: a pun, wordplay based on words that sound alike

Usefulness: 2 (it'd be more useful if I could think of a pun)

Logofascination: 1 (it's from an old Greek term, and there is something that appeals in the idea that puns are part of the human condition)

Immitigable

Meaning: that which cannot be mitigated, softened, lessened or extenuated.

Usefulness: 2 (It is slightly difficult to enunciate, but if you pull it off much gravitas is achieved: "Such behaviour is immitigable! The chocolate biscuits are sacrosanct, and we must not simply turn a blind eye." I suggest emphatic gestures to accompany the high dudgeon.)

Logofascination: 2

Bumdockdousse

Meaning: Urquhart's English name for pimpompet, which Cotgrave helpfully defines as "A kind of Game wherein three hit each other on the bumme with one of their feet." Later definitions call it an 'antick dance' rather than a game.

Usefulness: 2 (An incredibly apt metaphor for some meetings, although rather specific as to number. It lost points for sounding like a swearword, but could be useful as a swearword instead.)

Logofascination: 1 (a lovely example of how Sir Thomas worked: combining units - bum + dock (rump) + dousse (beat, strike) - to match the (non)sense and rhythm of the original.)

Fascicle

Meaning: a little bundle; in literary terms an instalment or a section of a greater work. Probably best known as a description of the hand-made booklets of poems left by Emily Dickinson.

Usefulness: 1 ("Of course, my email is but a fascicle." "She's really dropped her fascicle on this one.")

Logofascination: 2

Pepo

Meaning: fruit of the Cucurbitaceae family; they have a hard rind and lots of seeds in one space - includes melons, cucumbers, gourds, pumpkins.

Usefulness: 3 (foodie hipster points, maybe? or as a metaphor: all the brains of a pepo.)

Logofascination: 2 (I really have no idea why, though)

Gastromancy

Meaning: divination by the belly (referring to ventriloquism)

Usefulness: 1 (repurposed, this is an enormously useful word. For starters, my stomach can gastromantically divine all sorts of things - that it's time for elevenses, lunch, a martini, or all three.  However, it is more likely that I will use it to describe food: "Pork that good is unnatural: I suspect gastromancy.")

Logofascination: 1 (I have a thing for the -mancy list. I might need to limit myself to one a week.)

Profectitious

Meaning: from a parent or ancestor; originally of dowries from a father or other male ancestor.

Usefulness: 2 (can be used to describe family habits - my cricket addiction is profectitious; compliment babies politely - his nose is positively profectitious! - or to describe assorted mining and media dynasties. Or, of course, trustafarians.)

Logofascination: 2

Bezazz

Meaning: it's an alternate spelling (and pronunciation?) of pizazz, which is one of the mysterious origin unknown words.

Usefulness: 2 (hipster points: if people correct you, you can look at them pityingly and remark that it's an early variant. Sounds a bit like bees knees, beeswax, and other such melittological slang; so much so that I find myself having to resist the temptation to etymologise folksily.)

Logofascination: 3 (only escapes boring by virtue of having z three times)

Perjinkities

Meaning: niceties, proprieties

Usefulness: 2 (extra points for sounding lovely)

Logofascination: 2

Quiddity

Meaning: Quintessence. Thisness. The defining feature. The vibe, and various other hand-wavy concepts.

Usefulness: 1 (particularly in hand-wavy conversations)

Logofascination: 2 (comes with bonus synonym, haecceity)

Sciatherically

Meaning: of or like a sun-dial, or other instrument that cast shadows; in 1677 one could practice sciatherics, or the Art of Dialling.

Usefulness: 2 (it's rather adaptable: it could apply to speed - he moves sciatherically - or motion - progress has been sciatherical - or antiquity - my phone is sciatherically out of date)

Logofascination: 1 (for sheer obscurity)

Myrmidon

Meaning: a flunky, although wiktionary takes it one further: someone "who executes orders of a superior without protest or pity".

Usefulness: 1 (Let's face it, you either are one, or you'd like some)

Logofascination: 2

Barytonize

Meaning: The OED lists this as a word but does not define it; I shall write and complain.  In context, though, it's pretty clear we're talking about farting. Deep, profound, musical flatulence; sums up most of Rabelais, really. (Context below, if you don't believe me)

Usefulness: 1 (Particularly of meetings. To be exactly confusing you could say "This Urquhartian barytonizing must end. I call for a vote!")

Logofascination: 3 (juvenile fascination: 1)

Fletiferous

Meaning: causing weeping

Usefulness: 1 (maybe that's just me...)

Logofascination: 2

Frasmotic

Meaning: Invented for a Blackadder episode, ("Ink and Incapability") it's not yet in any official dictionaries, although this guy suggests 'so frazzled that one goes into a spasm.' There's a suggestion of frantic about it, as well.

Usefulness: 2 (rates very high in work applicability)

Logofascination: 2 (it's in Blackadder, and an episode about dictionaries at that)

Orthopantomography

Meaning: it's that dental x-ray (tomography, a particular kind of radiography involving planes, hence tomo - slice, section) where they can see all (a panorama) of your teeth an almost-straight (ortho) line. Was originally called ‘orthoradial pantomography’ which was 'shortened' to orthopantomography.

Usefulness: 3 (unless you work in dentistry or radiography, but it is an impressive sounding word)

Logofascination: 2 (there is something about all those Greek elements lined up together)