1. A person who is regarded as eccentric or mad
   "Everyone thought he was a wacko for believing in alien abductions";
   - nutter [Brit, informal], whacko [informal], nutbar [N. Amer, informal], nutjob [informal], wackadoodle [N. Amer, informal], nutcake [US, informal], basket case [informal], fruitcake [informal], whackjob [N. Amer, informal], wackjob [N. Amer, informal], mentalist [Brit, informal]

1. Insane, strange, eccentric or stupid
   "She's gone completely wacko since the accident";
   - balmy [archaic, slang], barmy [slang], bats [slang], batty [slang], bonkers [slang], buggy [N. Amer, slang], cracked [slang], crackers [slang], daft [Brit, slang], dotty [Brit, slang], fruity [slang], haywire [slang], kooky [slang], kookie [slang], loco [slang], loony [slang], loopy [slang], nuts [slang], nutty [slang], round the bend [slang], around the bend [slang], wacky [slang], whacky [slang], daffy [slang], dippy [slang], doolally [Brit, slang], daft as a brush [Brit, slang], potty [Brit, slang], round the twist [Brit, slang], dumbass [N. Amer, slang], nutsy [N. Amer, slang], barking mad [Brit, slang], mental [slang], barking [Brit, slang], bughouse [N. Amer, slang], cuckoo [slang]

Derived forms: wackoes, wackos

See also: insane, madman

Type of: dag [Austral, NZ, informal], eccentric, flake [N. Amer, informal], geek [informal], oddball [informal]

Encyclopedia: Wacko