What is the meaning of silly?

noun

• A word used for misbehaving children.
  • usage: "don't be a silly"

adjective

• Ludicrous, foolish.
  • usage: "gave me a cockamamie reason for not going"; "wore a goofy hat"; "a silly idea"; "some wacky plan for selling more books"
  • synonyms: cockamamie, cockamamy, goofy, sappy, wacky, whacky, zany
• Lacking seriousness; given to frivolity.
  • usage: "a dizzy blonde"; "light-headed teenagers"; "silly giggles"
  • synonyms: airheaded, dizzy, empty-headed, featherbrained, giddy, light-headed, lightheaded
• Inspiring scornful pity."how silly an ardent and unsuccessful wooer can be especially if he is getting on in years- Dashiell Hammett
  • synonyms: pathetic, ridiculous
• Dazed from or as if from repeated blows.
  • usage: "knocked silly by the impact"; "slaphappy with exhaustion"
  • synonyms: punch-drunk, slaphappy