thick as a whale omelette
thick as pig shit
rock-dumb
dumb
dumb as a stump
dumb as a post
dumber than a rock
dumb as dirt
retarded
shit-for-brains
dumber than a box of rocks
dumb as a doorknob
thick as two short planks
dumb as a box of rocks
thick as a plank
bee-brained
dumb as a bag of hammers
thick as mince
stupidass
dumb as nails
fuckwit
booger brain
shitwit
blockheadish
bodoh
stupidy
simpleminded
dumbassed
numbskulled
stupidish
witless wonder
mongtard
pillocky
dumb as a rock
fuckwittedness
retardation
thick
bull
one brick short of a full load
dumb as an ox
retardical
numbnut
dumbbutt
stockishly
dumb like a fox
fatheadedly
pratty
dopey
dumb fuck
fucktard