1(of an algebraic expression) consisting of three terms.
2 Biology (of a taxonomic name) consisting of three terms where the first is the name of the genus, the second that of the species, and the third that of the subspecies or variety.
noun
1an algebraic expression of three terms.
2 Biology a trinomial taxonomic name.
Origin:
late 17th century: from tri- 'three', on the pattern of binomial
trinomial in other Oxford dictionaries
Definition of trinomial in the US English dictionary
