n. In geometry, a solid bounded by plane faces.n. In optics, a multiplying glass or lens consisting of several plane surfaces disposed in a convex form, through each of which an object is seen; a polyscope.n. In bot.,in Hydrodictyon or water-net, one of the special angular cells with horn-like processes formed by the swarm-cells produced in the zygospore, within each of which a new cœnobium is developed.