n. 笨蛋, 轻佻的人, 轻率浮躁的人

[ noun ]
a person with confused ideas; incapable of serious thought
<noun.person>

birdbrain \bird"brain`\ n.
1. a person with confused ideas; incapable of serious
thought.

Syn: addle-head, loon.
[WordNet 1.5]