sil·ly 
(sĭlē)
(sĭlē)adj. sil·li·er, sil·li·est
1. Having or exhibiting a lack of good judgment or common sense; foolish. See Synonyms at foolish.
2. Lacking seriousness or responsibleness; frivolous: indulged in silly word play; silly pet names for each other.
3. Semiconscious; dazed: knocked silly by the impact.
[Middle English seli, silli, blessed, innocent, hapless, from Old English gesælig, blessed.]
silli·ly (sĭlə-lē) adv.
silli·ness n.