adj consisting of three terms; of or pertaining to trinomials; as, a trinomial root.
2. trinomial ·noun a quantity consisting of three terms, connected by the sign + or -; as, x + y + z, or ax + 2b - c2.
3. trinomial ·add. ·adj consisting of, or involving the use of, three terms; as, a trinomial systematic name specifying the genus, species, and variety.