Pronunciation: (rō-tā'shun in-vûr'zhun, -shun), [key] Crystall.
an axis of a crystal such that rotating about the axis and then inverting the crystal brings the crystal back to its original position. Also called symmetry axis of rotary inversion. Cf. symmetry element.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.