Post an obscure word, its definition, and use it in a sentence.

Just alright? I’m hurt.

Yogh : a letter used in middle english.

Alas poor Yogh urt, I knew him well.

Balderdash! That’s what it was. Only played it once, lo, these many years ago, but I still remember it.

Eleemosynary: having a charitable purpose.

“This restaurant is not an eleemosynary operation; you need to pay for your meal.”

And if you throw yourself out the window it is autodefenstration.
Despondent with his lot in life, Egbert autodefenestrated.

Feculant: feces like or having properties reminscient of feces.
I was forced to choose between the feculant out-house or the bush.

I once (verbally) used this word to describe a boss’s behavour in an unofficial workplace review. I sandwiched it between such comments as “joe” demonstrates a nearly unfailing commitment to ensuring staff anisodality (we all hate him), and “joe” seldom fails to register a phlegmiactic (indifferent) response to his motivational efforts.
Sad thing is they thought I was being supportive and complimentary…

I don’t work there anymore, BTW

FML

loquacious–full of excessive talk

Mrs. Gabble never stops talking; she doesn’t even have time to loquacious going.

pigsney- a term of edearment, especially for a girl

Hush, my little pigsney, and mama will rock you to sleep.

A word I learned from Maugham’s novel Of Human Bondage:
yclept - a past participle from an obsolete verb “clepe” meaning “to name”; yclept = named

The quote from Of Human Bondage ( http://www.gutenberg.org/files/351/351.txt ), added emphasis by yours truly

coprolite: Fossilized shit.

And while any sentence would only be technical (“He found a coprolite at the digging site”), I tend to agree with John Ciardi’s suggestion that the word makes a wonderful insult: “You third rate piece of coprolite.”

 This word became one of my favorites after its relation with [one of the coolest events](http://en.wikipedia.org/wiki/Defenestration_of_prague#Second_Defenestration_of_Prague)  we learned about in my European History class.

Callimastian - possessed of attractive breasts. “Slip me some sugar, my callimastian little rock pigeon”.

Infracaninophile - lover of the underdog. “There were not enough infracaninophiles in the US to make the recent movie a success”.

Regards,
Shodan

A term of address used by Screwtape in his final letter to Wormwood, too, and if not actually hapax legomenon (“a word known to have been used only once”), still pretty damned uncommon.

“Proparoxytone” - a word stressed on its antepenultimate syllable. “Talking of self-referentialism, it’s amusing to note that the word proparoxytone actually is one.”

Treppenwitz: A devastating rejoinder thought of only after leaving the scene of the debate.

“As always, I experienced treppenwitz just after the pit thread was closed.”

So which came first, this or l’esprit de l’escalier?

Philtrum: the vertical groove in the upper lip
Philster’s philtrum filled with sweat after a fast walk down Filbert Street in Philadelphia.

Hippopotamonstrosesquipedalian: an adjective used to describe extremely long words.

All of the other contestants in the spelling bee were given ten or twelve letter words, but the judges decided to saddle me with some fifty syllable hippopotamonstrosesquipedalinan stumper.

Crapulent- a hangover.

I was crapulent this morning.

Contarpulation - The act of contarpulating. “Jenny was in quiet contarpulation with her computer.”

Contarpulating - To contarpulate. “Ewww. They’re contarpulating in public!”

Contarpulate - The process of contarpulation. “We’re going to contarpulate 180 degrees after jumping through this rogue spatial dimension.”

I first misread this sentence as " David crouched outside the oven, waiting to achieve paneity." which I found quite amusing as a visual image.
Vexillologist - one who participates in the study of Flags.
I recall a rather vexing question posted in GQ about the alignment of the British Flag, which required the assistance of a few Vexillologists to help solve.