irresponsible
unconventional
carefree
happy-go-lucky
harum-scarum
slaphappy
Rosamund
bad-boy
big-framed
breezy
cavalier
cocky
conspiratorial
debonair
flirtatious
freewheel
go-as-you-please
intrepid
jocular
light-hearted
loose-lipped
madcap
negligent
nonchalant
profligate
quizzical
rakish
rollicking
self-mocking