CLOAK definition: 1. a loose outer piece of clothing without sleeves, that fastens at the neck, and is worn instead…. Learn more. A cloak is a long, loose outer garment, usually having a hood and no sleeves. It can also mean something that covers or conceals, or to hide or disguise something. See synonyms, antonyms, and usage examples of cloak . Cloak definition : a loose outer garment, as a cape or coat.. See examples of CLOAK used in a sentence. Definition of cloak in the Definitions.net dictionary. Meaning of cloak . What does cloak mean ? Information and translations of cloak in the most comprehensive dictionary definitions resource on the web.