Treppenwitz - blinding flashes of intellect…just a little too late.
verisimilitude
I got it from a book of extinct words. I love it because it describes something there is no modern word for, and it rhymes with purple. It’s a word that certainly deserves to be used.
Yar.
Vicissitudes (changes in daily life). I learned this word on an episode of ALF where he decides to join a monastery.
Defenestrate. Most of my windows don’t open, see.
Just one?
Slugabed. (or maybe weltanschauung.)
You learned that word from Alf? Really?
I’m a stickler for grammar and punctuation, but I absolutely love making up words. Of my vast pseudocabulary, these are the ones that don’t get used very often:
“Oxtabajillion” is my favorite imaginary number. It lies somewhere between a bajillion and a googol.
“Wazbob” is one of several generic names for function arguments that one of my comp sci professors came up with. “Well, what does this function take? It takes a number, a string, and a wazbob.”
“Snargit” and “Hargit” both serve as generic exclamations, but they do have technical definitions as well: In a collection of similar objects, the snargits are the objects that are plentiful but smaller in size, whereas the hargits are the objects that are less common but much larger in size. For example, if you’ve got a dozen chicken eggs and one ostrich egg, you might say “Could you bring me the eggs? Just the snargits, not the hargit.”
Conflate is the first word that comes to mind - one of my favorite words.
My imaginary large number of choice is “A Brazilian.” Obviously, it works better in verbal than in written communications.
Favorite real word I don’t get to use often? “Bloviate.” Usually only used during election cycles…
“Penultimate”
I try to use it whenever I can, but how often does second-to-last need to be labeled?
Crudité
Only simpletons use the common word “crudite”
Hey, I use “brazillion” too! I thought I was the only person who was clever enough to have come up with that 
Pejorative: love it.
Like Zophia, I love defenestrate. When I was a kid, I learned that the German word for window is fenster. Then when I ran into defenestrate, it cracked me up.
Yep, defenestration and sartorial.
I think you’d be surprised. At least once a month I find use for that word although, depending on my audience, I may use “next-to-last.” I also find use for the word antepenultimate (next-to-next-to-last.)
“Conflate” I use about once a week. It’s a very useful word.
I’ve always called “defenstrate” the Millard Fillmore of vocabulary, popular through its obscurity. Anybody with a reasonable interest in the English language knows that word. However, it is true that one rarely finds an opportunity to use it, unless you’re talking about Czech history.
bacchanalia
These are great! I also am a big fan of the Scientology use of the fake word “enterbulate”.
Years later, people would remember early May 2011, and the “crudité” wars started by monstro. Still splitting the board into two hateful factions decades later.
One I really like is melliflu (mellifluous in English).