Quote Originally Posted by bobert View Post
Google says means "to start to philosophize." The prefix за- has a range of meanings, but one is "begin"
First of all, yes, "заумничать" can be perfect form of verb "умничать" with "start-to-do" variant of perfectness (another example: "любить/полюбить" ("to love/start to love")).
This is what is written in dictionaries.
Note that this verb always expresses negative or humorous evaluation of action. He who "умничает" usually tries to look smarter than he is or, maybe, speaker doesn't respect him.
But there is problem: perfect form doesn't fit to your example.

But on the other side there is adjective "заумный" and noun "заумь". Direct translation can be "over-smart(ness)". General idea is the same as in "умничать", but "за-" enforces it, makes a little bit stronger.
By the rules of word-creation these can be converted in imperfect "заумничать" as the process, just a little bit stronger than "умничать".
It's not very common form, by it's nature it's just mistake, but I met it before. Like in "он заумничал целый час" - imperfect, just a little bit stronger form of "умничать".