unit cell definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
the smallest unit of structure of a crystal: it has sides parallel to the crystal axes and its exact repetition in three dimensions along these axes generates the space lattice of a given crystal
unit cell definition by American Heritage Dictionary
The smallest building block of a crystal, consisting of atoms, ions, or molecules, whose geometric arrangement defines a crystal's characteristic symmetry and whose repetition in space produces a crystal lattice.