Synonyms and related words :
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