silly
noun
a word used for misbehaving children
“don't be a silly”
adjective
ludicrous, foolish
“wore a goofy hat”
“a silly idea”
lacking seriousness; given to frivolity
“a dizzy blonde”
“light-headed teenagers”
inspiring scornful pity
“how silly an ardent and unsuccessful wooer can be especially if he is getting on in years”
dazed from or as if from repeated blows
“knocked silly by the impact”
“slaphappy with exhaustion”
Source: WordNet 3.1, Princeton University