>>'Twas brillig and the slithy tove
did gyre and gimble in the wabe.
All mimsy were the borogroves
and the mome raths outgrabe.

I have a question - what part of speech is 'outgrabe'?

Speaking of not having enough to do, she said ironically, pouncing on this eagerly...
I've just spent several minutes pondering, and my opinion is
that outgrabe is an adjective, because it is "obvious" that mimsy is an adjective, and thus the sentence would be balanced. Whatever a tove is, it gyred and gimbled, which are "obviously" verbs. Therefore it makes sense to me that
there would be two adjectives in the next sentence: the
borogroves were mimsy, and the mome raths were outgrabe.

I do have quite enough to do, but chose to have glorious fun with this instead!