1620s, "pertaining to geometry," shortened form of geometrical (q.v.). In reference to a style of ancient Greek pottery decoration characterized by straight lines and angles, and the associated culture, 1902.

in mathematics, 1941, probably from isometric (q.v.) on the model of geometry/geometric.

slightly earlier and more classical form of rhomb (q.v.), 1560s, from Late Latin rhombus, in the geometric sense.

"twenty-sided body," 1560s, from Latinized form of Greek eikosahedron, noun use of neuter of eikosahedros, from eikosi "twenty" + -hedra "seat, base, chair, face of a geometric solid," from PIE root *sed- (1) "to sit." Greek eikosi is from PIE *wikmti- "twenty," from *wi- "in half" (hence "two") + (d)kmti-, from root *dekm- "ten" (from PIE root *dekm- "ten"). Related: icosahedral.