merriam-webster defines (12. 050)

The lexicographers present another treasury of obscure words whose utility is delightfully questionable in many cases and at times borders on the linguistic equivalent of unuselessness. There were classics ultracrepidarian—opining or operating outside one’s scope of practice, and the derived terms serendipitist and anecdotage but moreover a lot of choice vocabulary that was new to us, like novercal, pertaining to or characteristic of stepmother (without an equivalent word for stepfathers, the opposite of avuncular, of uncles, with no term for aunts), an amatorcultist, “a little insignificant love—a pretender to affection,” useful to describe one’s worst ex, neighbourstained, hopefully never to be in one’s quiver (see also), backspang, a Scottish term for a loophole that allows one to back out of a deal and antihalian, a humbug, one opposed to festivities. Much more at the links above.