Ī'co-sa-hē'dron, n.

n. [Gr. εἴκοσι, twenty, and ἕδρα, seat, base, from ἕζεσθαι, to sit; Fr. icosaèdre.]

1. A solid of twenty equal sides or faces.
2. (Geom.) A regular solid, consisting of twenty equal and similar triangular pyramids whose vertices meet in the center of a sphere supposed to circumscribe it.