microprism means any of many very small prisms used, either to form a reflective surface, or to form an area in a camera's viewfinder that blurs if the image is not precisely in focus. Lexicurio rates it Sui generis — a strength score of 87 out of 100.
Etymology
From micro- + prism.
noun
- Any of many very small prisms used, either to form a reflective surface, or to form an area in a camera's viewfinder that blurs if the image is not precisely in focus