1) Around the bend 2) Avian 3) Balmy 4) Barmy 5) Bats 6) Batty 7) Bonkers 8) Buggy 9) Crackers 10) Crazy 11) Daft 12) Dotty 13) Haywire 14) Insane 15) Kookie 16) Kooky 17) Loco 18) Looney 19) Loopy 20) Mad 21) Mad as a march hare 22) Nutcase 23) Nuts 24) Nutso 25) Wacko 1) Around the bend 2) Balmy 3) Bananas 4) Bananas, crackers or nuts 5) Barmy 6) Bats 7) Batty 8) Bonkers 9) Buggy 10) Canadian clam 11) Certifiable, so to speak 12) Cockamamie 13) Cracked 14) Crackers 15) Crackers, nuts or bananas 16) Crazy 17) Crazy in the head 18) Daft 19) Dotty 20) Fruity 21) Harebrained 
Loony is also sometimes refers to Canadian dollars. ...
• (a.) See Luny.
Loon'y adjective See Luny . 
Loony is slang for an insane person.
loony, looney, luny 1. An offensive term that deliberately insults someone's intelligence and ability to act rationally. 2. someone who behaves in an eccentric or thoughtless way. 3. A shortening, informal, and alterated version of lunatic.