opaque
bull
retardical
dumb as an ox
one brick short of a full load
dumbbutt
thick
numbnut
numbskulled
simpleminded
dumbassed
dumbass
dunderheaded
dopey
bubbleheaded
muddlebrained
pratty
dumb as a bag of hammers
blockheadish
lamebrained
thick as mince
stupidy
bodoh
stupidass
dumb as nails
goofball
sill
stupidish
baka
dumb as a stump
rock-dumb
shit-for-brains
thick as pig shit
dumb as dirt
retarded
dumb as a post
dumber than a rock
dumb
boofheaded
thick as a whale omelette
dumbish
soft
goosish
twp
fool
dumb as a box of rocks
dumber than a box of rocks
crackbrained
thick as a plank
derpy
thick as two short planks
dumb as a doorknob
thickwitted
dym