This should be a poll! I am so excited about these words that I am commenting without reading other comments, so I'm sorry if someone else said that.

Okay, I knew: bibulous, adipose, adumbrate, lineaments, meniscus, penumbra, chiarascuro (because I took a film class once, ha), synecdoche, monad, afflatus, and Ziggurat. I could only define bibulous, lineaments, meniscus, chiaroscuro, synecdoche, and monad offhand, though. (Yes, I tested myself. Word geek!) A few of them are what I consider genuinely 19th century words; I've only ever seen "bibulous" in mid-19th (mostly women's!) writing.

This was such fun. Thank you.