A rage gland was a type of gland. In 2256, when the USS Discovery was examining a tardigrade-like alien's behavior for methods of supporting the war between the Federation and the Klingon Empire, Commander Ellen Landry suggested to Michael Burnham that the creature, nicknamed "Ripper", might have had a rage gland or a venom sac that might prove advantageous in their effort to weaponize it. (DIS: "The Butcher's Knife Cares Not for the Lamb's Cry")