1. (a.) Of or pertaining to the chin; genian; as, the mental nerve; the mental region.

2. (n.) A plate or scale covering the mentum or chin of a fish or reptile.

3. (a.) of or pertaining to the mind; intellectual; as, mental faculties; mental operations, conditions, or exercise.

abnormal abstract affective balmy bananas barmy batty bereft of reason bonkers brainsick cerebral certifiable characteristic cogitative cognitive concentrating concentrative conceptive conceptual conceptualized constitutional contemplating contemplative crackbrained cracked crackers crazed crazy daft deliberating deliberative deluded demented deprived of reason deranged disoriented dispositional distraught disturbed emotional endopsychic excogitating flighty fruity hallucinated ideative ideological immaterial innate inner insane intellectual intelligent internal introspective irrational loco loony lunatic mad maddened maniac manic mazed meditating meditative mentally deficient mentally ill meshuggah mindless moon-struck museful musing noetic non compos non compos mentis noological not all there not right nuts nutty odd of unsound mind off pensive perceptual phrenic pondering prehensive psychic psychical psycho psychologic psychological psychotic queer rational reasoning reasonless reflecting reflective ruminant ruminating ruminative screwy senseless serious sick sober speculative spiritual stark-mad stark-staring mad strange subjective telepathic temperamental tetched theoretical thinking thought thoughtful touched unbalanced unhinged unsane unsettled unsound unstable wandering wistful witless