pentaprism

noun

pen·​ta·​prism

ˈpentə+ˌ-

: a pentagonal prism having one angle 90° and the others 112° 30′, producing a constant deviation of 90° for any wavelength, and used as a reflector in range finders

Word History

Etymology

penta- + prism

Love words?

You must — there are over 200,000 words in our free online dictionary, but you are looking for one that’s only in the Merriam-Webster Unabridged Dictionary.

Start your free trial today and get unlimited access to America's largest dictionary, with:

• More than 250,000 words that aren't in our free dictionary
• Expanded definitions, etymologies, and usage notes
• Advanced search features
• Ad free!