trimorph

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A substance that occurs in three distinct crystalline forms.
2. n. One of the crystalline forms in which a trimorphic substance occurs.

Century Dictionary and Cyclopedia

1. n. In crystallography, a substance which exhibits trimorphism, or one of the three forms which such a substance presents: thus the term may be applied to titanium dioxid, or to rutile, one of its three forms of crystallization.

GNU Webster's 1913

1. n. A substance which crystallizes in three distinct forms, or which has three distinct physical states; also, any one of these distinct forms. See trimorphism, 1.