prism

1. An object having the shape of a geometrical prism (sense 1).
2. A cutting (“open passage at a level lower than the surrounding terrain, dug for a canal, railway, or road to go through”) or an embankment shaped like a prism (sense 1) or a number of prisms, such that its volume can be easily calculated.
3. A crystal in which the faces are parallel to the vertical axis.
4. A transparent block in the shape of a prism (sense 1), typically with triangular ends, used to reflect or refract light.
5. A retroreflector (“device which reflects light back to its source with minimal scattering”) which is usually attached to a surveying pole as a target for a total station which emits a light beam at the device and calculates how long it takes to be reflected back in order to measure distance.
6. A perspective that colours one's perception. (figuratively)

Plural prisms