adrift
afloat
alternating
amorphous
blank
brainless
capricious
changeable
changeful
dazed
desultory
deviable
dippy
dizzy
dopey
eccentric
empty
empty-headed
empty-minded
empty-pated
empty-skulled
erratic
fast and loose
featherbrained
featherheaded
fickle
fitful
flibbertigibbet
flickering
flighty
flitting
fluctuating
fluttery
freakish
frivolous
gaga
giddy
giddy-brained
giddy-headed
giddy-pated
giddy-witted
harebrain
harebrained
hollow
impetuous
impulsive
inane
inconsistent
inconstant
indecisive
haywire