brainless
headless
artless
awkward
blankminded
callow
dumb
empty
empty-headed
fatuous
foolish
gauche
green
groping
half-assed
ignorant
impenetrable
inadept
inane
inapt
inattentive
inefficient
inept
inexperienced
inexpert
innocent
insensate
irrational
know-nothing
lackbrained
lean-minded
lean-witted
mediocre
mindless
naive
nescient
not bright
of little brain
pea-brained
pedestrian
pin-brained
poor
raw
reasonless
senseless
simple
skill-less
slackminded
slackwitted
apathetic
disingenuous
illogical
incompetent
ineffective
irrelevant
irresponsible
lax
sluggish
thoughtless
uncaring
uneducated
unenlightened
uninterested
uninteresting
unlearned
unreliable
unskilled
unthinking
unwise
clever
intelligent