dull
dumb
foolish
futile
ill-advised
irrelevant
laughable
ludicrous
naive
senseless
shortsighted
simple
trivial
dummy
loser
rash
thick
unintelligent
brainless
dazed
deficient
dense
dim
doltish
dopey
gullible
half-baked
half-witted
idiotic
imbecilic
inane
indiscreet
insensate
meaningless
mindless
moronic
nonsensical
obtuse
out to lunch
pointless
puerile
simpleminded
slow
sluggish
stolid
stupefied
thick-headed
unthinking
witless