simpleminded (?.)
- arrested
- artless
- babbling
- backward
- blithering
- bluff
- blunt
- born yesterday
- burbling
- candid
- childlike
- confiding
- crackbrained
- cracked
- crazy
- cretinistic
- cretinous
- dim-witted
- direct
- dithering
- driveling
- drooling
- dull
- feebleminded
- frank
- guileless
- half-baked
- half-witted
- idiotic
- imbecile
- imbecilic
- ingenu
- ingenuous
- innocent
- maundering
- mentally defective
- mentally deficient
- mentally handicapped
- mentally retarded
- mongoloid
- moronic
- naive
- not all there
- open
- openhearted
- outspoken
- plain
- retarded
- simple
- simplehearted
- simpletonian
- sincere
- single-hearted
- single-minded
- slobbering
- slow
- slow-witted
- subnormal
- trustful
- trusting
- unguarded
- unreserved
- unsophisticated
- unsuspicious
- unwary
