WordNet sense 1 (concerned with trivialities):

trivial

WordNet sense 2 (intended primarily as entertainment; not serious or profound):

light

WordNet sense 3 (silly or trivial):

idle

WordNet sense 4 (showing inappropriate levity):

flippant, light-minded

WordNet sense 5 (guided by whim and fancy):

flighty

WordNet sense 6 (lacking seriousness; given to frivolity):

dizzy, giddy, silly, light-headed