(1):
(n.) A transparent body, with usually three rectangular plane faces or sides, and two equal and parallel triangular ends or bases; - used in experiments on refraction, dispersion, etc.
(2):
(n.) A solid whose bases or ends are any similar, equal, and parallel plane figures, and whose sides are parallelograms.
(3):
(n.) A form the planes of which are parallel to the vertical axis. See Form, n., 13.