1 : of, relating to, or resembling a goose
2 : stupid, silly ridiculous
3 : noun a crystalline base found in the muscles of birds; methyl-carnosine
1: The beast’s anserine call noises confused the group, as there was no reason for a geese in the cave.
2: Tomal’s anserine behavior embarrassed the rest of the party at the event.
I could see uses for the first two meanings in a game, but only if you a) know your party or dm will recognize the term, or b) want to confuse them if they don’t. I suppose it could also be a diction choice of an NPC (like many of the words in this list so far), perhaps for the wizard who spends more time in books than with people.