4. (Naut.) (a) A boat used by ships of war. (b) A fast sailing vessel with one mast, rigged in most essentials like a sloop. A cutter is narrower end deeper than a sloop of the same length, and depends for stability on a deep keel, often heavily weighted with lead. (c) A small armed vessel, usually a steamer, in the revenue marine service; -- also called revenue cutter.