dumbish
stupidish
sillyish
numbskulled
dumbassed
simpleminded
thickhead
numbnut
dumb as an ox
thick
dumbbutt
retardical
bull
one brick short of a full load
dumb as a rock
dopey
blockheadish
opaque
bodoh
stupidy
stupidass
semistupid
thick as mince
semidumb
pratty
muddlebrained
dumbishly
stupidly
tomfool
airheaded
dumbass
dunderheaded
thickwitted
doltishly
dumben
dumb as nails
baka
pillocky
dym
boofheaded
lamebrained
dumber than a box of rocks
sill
subtepid
goofball
bubbleheaded
thick as a plank
dumb as a doorknob
dumb as a box of rocks
thick as two short planks
dumb
dumb like a fox
derpy
nonsense
stupidicy
stockishly
daft
stuuupid
foppery
dumbfuckery
fatheadedly
twp
fuckheaded
goosish
fool
soft
thick as a whale omelette
dumb as a post
dumb as dirt
rock-dumb
hash
fatuitous
retarded
cockamamy
bee-brained
shit-for-brains
dumber than a rock
dumb as a stump
thick as pig shit
headslapper
lamish
dumbfounder
anserous
anserine
beetlebrain
dumb bunny
dullwit
ass
dope
blubberbrain
dingwad
doorknob
boaby
booby
blockhead
bubblehead
sawney