loony (
http://definr.com/loony)
adj : informal or slang terms for mentally irregular [syn:
balmy,
barmy,
bats,
batty,
bonkers,
buggy,
cracked,
crackers,
daft,
dotty,
fruity,
haywire,
kooky,
kookie,
loco,
loopy,
nuts,
nutty,
wacky]
n : someone deranged and possibly dangerous [syn:
crazy,
looney,
weirdo]