1. 
[syn: airheaded, dizzy, empty-headed, featherbrained, giddy, light-headed, lightheaded, silly]
The Collaborative International Dictionary of English v.0.48:
airheaded \airheaded\ adj.
   1. lacking seriousness; given to frivolity; scatterbrained;
      stupid; simple-minded; as, airheaded teenagers. Contrasted
      with serious, solemn
   Syn: dizzy, empty-headed, featherbrained, giddy, lightheaded,
        light-headed, silly
        [WordNet 1.5]
WordNet (r) 3.0 (2006):
airheaded
    adj 1: lacking seriousness; given to frivolity; "a dizzy
           blonde"; "light-headed teenagers"; "silly giggles" [syn:
           airheaded, dizzy, empty-headed, featherbrained,
           giddy, light-headed, lightheaded, silly]