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