Definitions for BATSbæts
Random House Webster's College Dictionary
Category: Status (usage)
Origin of bats:
1915–20; appar. bat2+ -s3
balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kooky, kookie, loco, loony, loopy, nuts, nutty, round the bend, around the bend, wacky, whacky(adj)
informal or slang terms for mentally irregular
"it used to drive my husband balmy"
You must be bats to go out in the cold without a coat on.