cerebrally challenged
intellectually challenged
half-witted
mentally challenged
drool bucket
fool
fuckhead
hammerhead
blockhead
dumbass
shithead
muttonhead
lunkhead
knucklehead
dunce
loggerhead
divvie
bonehead
numskull
dunderhead
lackbrain
unintelligence
blonde
doltish
hammer-headed
underwitted
not the sharpest tool in the box
not the sharpest knife in the drawer
not the sharpest tool in the shed
ungenius
monkey
midget-minded
vacancy
gormless
dipshidiot
stupidass
dirtbrain
fuckwitted
stun
smooth-brained
pinheadedness
idiot
half-brained
light-witted
underbrained
duuumb
subnormal
unknowledgeable
thickheaded
Boeotian