WordWeb Online

1. Having or causing a whirling sensation; liable to falling
   "had a headache and felt giddy"; "a giddy precipice"
   - dizzy, woozy, vertiginous
    
2. Lacking seriousness; given to frivolity
   - airheaded, dizzy, empty-headed, featherbrained, light-headed, lightheaded, silly

1. Make or become giddy

Derived forms: giddiest, giddies, giddying, giddier, giddied

See also: frivolous, giddily, giddiness, ill, sick