[ 'prɪz(ə)m ]
■ noun
1》 Geometry a solid geometric figure whose two ends are similar, equal, and parallel rectilinear figures, and whose sides are parallelograms.
2》 Optics a transparent object in this form, especially one with triangular ends used to separate white light into a spectrum of colours.
Origin
C16: via late L. from Gk ~a 'thing sawn', from prizein 'to saw'.