Some of my favorites from our YWYS Facebook posts:
Aeipathy: Continued passion, unyielding
In a sentence: His aeipathy for birdwatching was his most defining trait.
In a sentence: Judge Judy is often acrasial, but rightly so.
Welkin: The upper sky; “vault” of heaven
In a sentence: Frustrated by her experience with the DMV, she sighed so loudly that it was heard in the welkin.
Schismarch: Founder of a schism
In a sentence: She fancies herself a schismarch, but she’s just playing low-level office politics.
Namelings: Those bearing the same name
In a sentence: In the 1970s, male namelings in a senior high school class were often called Bob, Jim, or Mike. Now it’s Jacob, Joshua, or Ethan. And 17 years from now it will be Liam, Noah, or Elijah.