dumb as a box of rocks
Lacking all sense
Dumb as a box of rocks describes someone extremely stupid or slow-witted.
The comparison to inanimate objects emphasizes complete absence of intelligence: He's nice enough, but dumb as a box of rocks.
The phrase belongs to a family of similar expressions—dumb as a post, dumb as a doorknob—all suggesting the mental capacity of objects incapable of thought.
- unintelligentLacking cognitive ability
- dumb as a bag of hammersExtremely unintelligent person
- dumb as a postProfoundly unintelligent person
- not the sharpest knife in the drawerUnintelligent, said gently
- ignorantLacking knowledge or awareness
not the sharpest tool in the shed · not the brightest bulb · sharp as a bowling ball · stupid · thick as a brick · fool · slow-witted · empty-headed · lights are on but nobody's home · dim-witted · dim · thick-headed · idiot · dummy · dumbbell · dope · dull as dishwater · dodo
dumb as a box of rocksbrilliant
Intensely bright or gifted
genius · intelligent · smart as a whip · sharp as a tack · clever
dumb as a box of rockssharp as a tack
Extremely intelligent and alert
smart cookie · bright spark · quick on the uptake · knows their stuff · cream of the crop
dumb as a box of rockssharp
Fine-edged, or astute
perceptive · astute · shrewd · keen · quick on the uptake