noun

• (law) An order or rule forbidding discussion of a case or subject.
• (figurative) Any suppression of freedom of speech.
  "Civil Court blocks PM's gag on free speech"
• (film) a device or trick used to create a practical effect; a gimmick
  "On Hacksaw Ridge, Oliver and his team of effects artisans devised gags for that spectacular flamethrower shot along with other devastating body and bullet hits, and several mortar and full-scale explosions, all aimed at communicating the reality of battle."
• (archaic) A mouthful that makes one retch or choke.
  "L. has recorded the repugnance of the school to gags, or the fat of fresh beef boiled, and sets it down to some superstition."

verb

• (intransitive) To experience the vomiting reflex.
  "He gagged when he saw the open wound."
• (transitive) To cause to heave with nausea.
  "His empty stomach was suddenly full of butterflies, and for the first time since arriving here at scenic Durkin Grove Village, he felt an urge to gag himself. He would be able to think more clearly about this if he just stuck his fingers down his throat […]"
• (transitive) To restrain someone's speech by blocking his or her mouth.
  "“[…] Captain Markam had been found lying half-insensible, gagged and bound, on the floor of the sitting-room, his hands and feet tightly pinioned, and a woollen comforter wound closely round his mouth and neck ; whilst Mrs. Markham's jewel-case, containing valuable jewellery and the secret plans of Port Arthur, had disappeared. […]”"
• (transitive) To pry or hold open by means of a gag.
  "1917, Francis Gregor (translator), De Laudibus Legum Angliae, Sir John Fortescue, written 1468–1471, first published 1543. […] some have their mouths gagged to such a wideness, for a long time, whereat such quantities of water are poured in, that their bellies swell to a prodigious degree […]"