Definition of umbrella

• n. - A shade, screen, or guard, carried in the hand for sheltering the person from the rays of the sun, or from rain or snow. It is formed of silk, cotton, or other fabric, extended on strips of whalebone, steel, or other elastic material, inserted, or fastened to, a rod or stick by means of pivots or hinges, in such a way as to allow of being opened and closed with ease. See Parasol.
• n. - The umbrellalike disk, or swimming bell, of a jellyfish.
• n. - Any marine tectibranchiate gastropod of the genus Umbrella, having an umbrella-shaped shell; -- called also umbrella shell.