Definition: stupid, silly
Here we have a lovely example of a word which began its life (in our language, at least) with a figurative meaning, and only took on a literal one after more than a century of use. Anserine comes from the Latin anser, meaning "goose." The word is indeed used on occasion to mean "resembling a goose," but the 'silly as a goose' sense preceded this by a considerable length of time.
I am not of such anserin stupidity, but that I could make as ignominions at reorsion upon my adversary.
— John Menzies, Roma Mendax, 1675