retarded
apish
arrested
asinine
babbling
backward
batty
befooled
beguiled
besotted
blithering
brainless
buffoonish
burbling
cockeyed
crackbrained
cracked
crazy
credulous
cretinistic
cretinous
daffy
daft
dazed
dim-witted
dithering
dizzy
doting
driveling
drooling
dull
dumb
fatuitous
fatuous
feebleminded
flaky
fond
fool
foolheaded
foolish
fuddled
futile
gaga
goofy
gulled
half-baked
half-witted
idiotic
imbecile
imbecilic
inane
Wikipedia article on mental retardation
moron
addle-brained
alpha-numeric
bumble
dog-faced
drug-crazed
gullible
insensitive
long-snouted
mahogany-faced
mean-tempered
musclebound
octogenarian
orang-outang
paleoclimate
replacev'
sociocentric
statist
undiplomatic
unmannerly
unmilitary
witless