submoron
subintellectual
subnormal
nonintellectual
submoronic
fool
divvie
birdbrain
drool bucket
stun
monkey
four oh four
lackbrain
subexpert
dunderhead
dunce
blockhead
hammerhead
fuckhead
knucklehead
muttonhead
shithead
bonehead
numskull
lunkhead
dumbass
idiot
loggerhead
lackluster
amateur
dimwit
honyock
dipstick
simple
wally
gobemouche
gobe-mouche
simpleton
doltish
ungenius
ignoranus
dropkick
airhead
not the sharpest knife in the drawer
nonphilosopher
rube
concrete-head
dipshidiot
muff
not the sharpest tool in the shed
nonvisionary
not the sharpest tool in the box
dull
dumb genius
yokel
jasper
brainlet
stupid
bumpkin
hayseed
hick
chawbacon
dumbling
yahoo
half-wit
unteachable
halfwit
innumerate
nondescript
jabroni
dink
coxcomb
fledgling
half-witted
intellectually challenged
cerebrally challenged
jack of all trades, master of none
meathead
cockbag
harebrain
simp
fuzznuts
addle-brain
philosophe
mouth breather
glaik
crackhead
muggle
addlehead
dirtbrain
doilem
fuzznut
mooncalf
git
short-witted
blinkard
doofbag
cacophrenic