irrational
animal
arbitrary
blank
blankminded
brainless
brutal
brute
brutish
calm
capricious
careless
emotionalistic
emotive
empty
empty-headed
fatuous
foolish
hammy
headless
heedless
histrionic
hysteric
ignorant
inadvertent
inane
incogitant
inconsiderate
inept
insensate
lackbrained
lean-minded
lean-witted
melodramatic
mindless
nirvanic
nonrational
not bright
oblivious
of little brain
overemotional
passive
pea-brained
pin-brained
quietistic
reasonless
relaxed
sensational
sensationalistic
causeless
deep-seated
fanatical
frenzied
groundless
implacable
impotent
instinctive
passionate
pent-up
primal
senseless
unbridled
unconquerable
uncontrollable
undisguised
undying
unthinking
rational