isomorph definitions Merriam Webster's noun see isomorphous Oxford Reference Dictionary ... organism. Etymology: ISO- + Gk morphe form Webster's 1913 Dictionary Isomorph I"so*morph, n. [See Isomorphous.] A substance which is ... another in crystalline form and composition. Webster's 1913 Dictionary Isomorph I"so*morph, n. (Biol.) An animal, plant, or group ...