thick as mince
thick as a whale omelette
dumb as a stump
dumber than a rock
dumb as a post
dumb
thick as pig shit
retarded
rock-dumb
shit-for-brains
thick as two short planks
dumb as a box of rocks
dumbassed
simpleminded
dumb as a doorknob
numbskulled
dumb like a fox
dumber than a box of rocks
thick as a plank
muddlebrained
opaque
baka
dunderheaded
thickheaded
bull
dumbbutt
one brick short of a full load
retardical
puzzlewit
cockbrain
thick
numbnut
dumbnut
dumb as an ox
dumbass
dumb as a bag of hammers
asinine
thickhead
dumben
inane
fatuous
stupidly
bubbleheaded
sohai
tomfool
pillocky
lamebrained
doltishly
trolltard