/ ˈprɪzəm; NAmE / noun
1.
( geometry ) a solid figure with ends that are parallel and of the same size and shape, and with sides whose opposite edges are equal and parallel
2.
a transparent glass or plastic object, often with ends in the shape of a triangle, which separates light that passes through it into the colours of the rainbow
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WORD ORIGIN
late 16th cent.: via late Latin from Greek prisma thing sawn, from prizein to saw.