'Metamer' definitions:

Definition of 'Metamer'

From: GCIDE

Metamer \Met"a*mer\, n. [See Metamere.] (Chem.) Any one of several metameric forms of the same substance, or of different substances having the same composition; as, xylene has three metamers, viz., orthoxylene, metaxylene, and paraxylene; an isomer. [1913 Webster]