mentally challenged
half-witted
idiot
dirtbrain
half-brained
cerebrally challenged
intellectually challenged
halfwit
unintelligence
not the sharpest tool in the shed
not the sharpest knife in the drawer
stupidass
not the sharpest tool in the box
underbrained
vacancy
dense
subnormal
stun
dimwit
fool
unintelligent
stupid
unbright
drool bucket
divvie
lackluster
simple
subnormality
simpleton
light-witted
dull
nonintelligence
subexpert
worse
slow-witted
nonintelligent
short-witted
room-temperature IQ
underwitted
simple-mindedly
imbecile
shithead
dumbass
fuckhead
hammerhead
dunce
muttonhead
loggerhead
changeling
cretin