Light-minded \Light"-mind`ed\ (l[imac]t"m[imac]nd`[e^]d), a.
1. Unsettled; unsteady; volatile; not considerate.
[1913 Webster]
2. showing inappropriate levity. [WordNet sense 1]
Syn: flippant.
[WordNet 1.5] -- {Light"-mind`ed*ness}, n.
[1913 Webster]