noun Crystallography.

a substance existing in three structurally distinct forms; a trimorphous substance.
any of the three forms.

Origin of trimorph

First recorded in 1905–10, trimorph is from the Greek word trímorphos having three forms. See tri-, -morph Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

British Dictionary definitions for trimorph



a substance, esp a mineral, that exists in three distinct forms
any of the forms in which such a structure exists
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012