solid solution

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A homogeneous crystalline structure in which one or more types of atoms or molecules may be partly substituted for the original atoms and molecules without changing the structure.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun physics Any homogenous crystalline solid, consisting of more than one type of molecule or atom randomly dispersed, in which the structure is independent of its composition.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a homogeneous solid that can exist over a range of component chemicals; a constituent of alloys that is formed when atoms of an element are incorporated into the crystals of a metal