Meaning of no-no

no-no

Pronunciation: (nō'nō"), [key]
— pl. -nos, -no's.
  1. anything that is forbidden or not advisable, as because of being improper or unsafe: If you want to lose weight, rich desserts are a no-no.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.