—n. 1. a very large person, animal, or thing.
2. See jumbo jet. 3. U.S. Naut. a. a forestaysail having a boom (jum'bo boom") along its foot, used esp. on schooners.
b. a sail used in place of a course on a square-rigged ship, having the form of an isosceles triangle set apex downward.
c. a narrow triangular sail set point downward in place of a foresail on a topsail schooner.