say it: PRIZ-uhm
prism is a noun meaning "a polyhedron with two congruent and parallel faces (the bases) and whose lateral faces are parallelograms". It carries 2 recorded senses.
a polyhedron with two congruent and parallel faces (the bases) and whose lateral faces are parallelograms
optical device having a triangular shape and made of glass or quartz; used to deviate a beam or invert an image
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for prism come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.