unintelligent
stupid
underbrained
unintelligence
vacancy
stupidass
not the sharpest tool in the box
not the sharpest knife in the drawer
not the sharpest tool in the shed
lackluster
vacant
mindless
vacuous
nonintelligence
simple
simpleton
halfwit
dense
weak
nonintelligent
incapacity
acognitive
gormless
unskillfulness
dyscompetence
brainless
headless
mentally challenged
feeble-minded
insufficiency
shallow
inadequacy
nondiligence
subnormal
dysrationalia
half-brained
dim
dimwit
inexpertness
idiot
unlearned
subnormality
unlettered
retardation
backwardness
nescient
mental retardation
ignorant
slowness
dirtbrain
intellectually challenged
light-witted
cerebrally challenged
fumbling
bungling
incompetent
clumsy
dull
nonproficiency
obtuse
ineffective
unproficiency
stun
unbright
dumb
slow
improficiency
uncomprehending
insightlessness
indocible
underwitted
skillessness
imbecile
retard
changeling
sophomania
cretin
clueless
half-wit
moron
inexpertise
naive
amateurish
inexpert
unskilled
nonintellectual
amateur
purblind