n.  1.  (Alg.) An expression consisting of two terms connected by the sign plus (+) or minus (); as,  
a.  1.  Consisting of two terms; pertaining to binomials;  
2.  (Nat. Hist.) Having two names;  used of the system by which every animal and plant receives two names, the one indicating the genus, the other the species, to which it belongs.

Noun  1.  binomial  a quantity expressed as a sum or difference of two terms 
Adj.  1.  binomial  relating to binomials; "binomial expression" 
2.  binomial  consisting of two names or terms; "binomial nomenclature" 