1. lacking seriousness
given to frivolity

e.g. a dizzy blonde
light-headed teenagers
silly giggles

Synonym: airheadeddizzyempty-headedfeatherbrainedgiddylight-headedsilly

2. weak and likely to lose consciousness

e.g. suddenly felt faint from the pain
was sick and faint from hunger
felt light in the head
a swooning fit
light-headed with wine
light-headed from lack of sleep

Synonym: faintlightswooninglight-headed