tri·no·mi·al 
(trī-nōmē-əl)
(trī-nōmē-əl)adj.
1. Consisting of three names or terms, as a taxonomic designation.
2. Mathematics Consisting of three terms.
n.
1. A three-part taxonomic designation indicating genus, species, and subspecies or variety, such as Brassica oleracea botrytis, the cauliflower.
2. Mathematics An algebraic expression consisting of three terms connected by plus or minus signs, such as x2 + 4x -3.
[TRI- + (BI)NOMIAL.]
tri·nomi·al·ism n.