D defs.my
Entry 1 sense Webster, 1913

no-no

· no·-no · IPA
01 n. Something improper, unethical, inadvisable, or illegal; as, salt is a no-no for someone after a heart attack.
  1. 1.
    Something improper, unethical, inadvisable, or illegal; as, salt is a no-no for someone after a heart attack.[informal]