[syn: airheaded, dizzy, empty-headed, featherbrained, giddy, light-headed, lightheaded, silly]
The Collaborative International Dictionary of English v.0.48:
Light-headed \Light"-head`ed\ (l[imac]t"h[e^]d`[e^]d), a.
   1. Disordered in the head; dizzy; feeling faint; delirious.
      [WordNet sense 1] --Walpole.
   Syn: faint, swooning, lightheaded.
        [1913 Webster + WordNet 1.5]
   2. Thoughtless; heedless; volatile; unsteady; fickle; loose;
      lacking seriousness; given to frivolity; as, light-headed
      teenagers. [WordNet sense 2] "Light-headed, weak men."
      --Clarendon.
   Syn: airheaded, dizzy, empty-headed, featherbrained, giddy,
        lightheaded, silly.
        [1913 Webster + WordNet 1.5] -- Light"-head`ed*ness,
        n.
        [1913 Webster]
WordNet (r) 3.0 (2006):
light-headed
    adj 1: weak and likely to lose consciousness; "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" [syn:
           faint, light, swooning, light-headed,
           lightheaded]
    2: lacking seriousness; given to frivolity; "a dizzy blonde";
       "light-headed teenagers"; "silly giggles" [syn: airheaded,
       dizzy, empty-headed, featherbrained, giddy, light-
       headed, lightheaded, silly]