arrested
babbling
backward
blithering
burbling
crackbrained
cracked
crazy
cretinistic
cretinous
dithering
driveling
drooling
half-baked
half-witted
idiotic
imbecile
imbecilic
maundering
mentally defective
mentally deficient
mentally handicapped
mentally retarded
moronic
not all there
retarded
simple
simpleminded
simpletonian
slobbering
subnormal