retardation
fuckwittedness
boobery
dipshittery
stupidicy
dumbfuckery
foppery
wearishness
numskullery
dunderheadism
stockishness
dunderheadedness
brain damage
thickheadedness
shtus
blondeness
headslapper
bozon
stupids
dumb as a bag of hammers
stuuupid
bee-brained
lamebrained
idiotist
duuumb
stupidity
jackassism
derp
shit-for-brains
dumb
shitwit
rock-dumb
thick as a whale omelette
dumb as dirt
thick as pig shit
fuckwit
dumber than a rock
dumb as a stump
witless wonder
booger brain
retarded
dumb as a post
opaque
der
mongtard
muddlebrained
stupidly
damnfool
bodoh
stupidy