Source : Webster's Revised Unabridged Dictionary (1913)

Light-headed \Light"-head`ed\ (-h[e^]d`[e^]d), a.
   1. Disordered in the head; dizzy; delirious. --Walpole.

   2. Thoughtless; heedless; volatile; unsteady; fickle; loose.
      ``Light-headed, weak men.'' --Clarendon. --
      {Light"-head`ed*ness}, n.

Source : WordNet®

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}, {lightheaded}]
     2: lacking seriousness; given to frivolity; "a dizzy blonde";
        "light-headed teenagers"; "silly giggles" [syn: {airheaded},
         {dizzy}, {empty-headed}, {featherbrained}, {giddy}, {lightheaded},
         {silly}]