"whacky" in the adjective sense
1. goofy, silly, wacky, whacky, zany
ludicrous, foolish
"wore a goofy hat"
"a silly idea"
"some wacky plan for selling more books"
2. 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
informal or slang terms for mentally irregular
"it used to drive my husband balmy"
Source: WordNet® (An amazing lexical database of English)
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