bats(s = adj.all) around the bend, balmy, barmy, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kookie, kooky, loco, loony, loopy, nuts, nutty, round the bend, wacky, whacky - informal or slang terms for mentally irregular; "it used to drive my husband balmy"

   Crazy; insane; loony; demented; batty. [PJC]

bats, predic.adj. sl. crazy.

Etymology:
f. phr. (have) bats in the belfry: see BAT(2)