/jum"boh/ , n. , pl. jumbos , adj. Informal.
n.
1. a very large person, animal, or thing.
2. See jumbo jet .
3. U.S. Naut.
a. a forestaysail having a boom (jumbo 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.
adj.
4. very large: the jumbo box of cereal.
[ 1800-10; orig. uncert.; popularized as the name of a large elephant purchased and exhibited by P.T. Barnum in 1882 ]