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