dim
nonintelligent
unintelligent
dull
nonsmart
unsmart
lackluster
unsmartness
stupidass
unbright
vacancy
unintellectual
unclever
underbrained
gormless
ungroomed
half-witted
unintelligence
short-witted
ungeeky
stupid
nonsavvy
not the sharpest tool in the box
not the sharpest knife in the drawer
slow-witted
halfwit
not the sharpest tool in the shed
intellectually challenged
cerebrally challenged
unintellectualized
mindless
vacuous
light-witted
vacant
doltish
unastute
cloistered
mentally challenged
ungenius
fool
sharp as a bowling ball
unskillful
uninsightful
noninsightful
simple-mindedly
unknowledgeable
nonintellectual
subintellectual
unreasonably
uncleverness