bee-brained
dumber than a rock
shit-for-brains
dumb as a stump
dumb
retarded
thick as a whale omelette
dumb as dirt
dumb as a post
rock-dumb
thick as pig shit
thick as mince
stupidass
dumb as a box of rocks
thick as two short planks
dumber than a box of rocks
dumb as a doorknob
thick as a plank
dumb as a bag of hammers
pillocky
dumb as nails
blockheadish
bodoh
stupidy
pratty
dumb as a rock
dumb like a fox
numbskulled
dumbassed
simpleminded
opaque
asinine
stupidish
fucktarded
inane
fatuous
dopey
chuckleheaded
dym
numbnut
dumbbutt
fatuitous
dumb as an ox
one brick short of a full load
retardical
thick
bull
dead from the neck up