Source : Webster's Revised Unabridged Dictionary (1913)

Multinomial \Mul`ti*no"mi*al\, n. & a. [Multi- + -nomial, as in
   binomial. See {Binomial}.] (Alg.)
   Same as {Polynomial}.

Source : WordNet®

multinomial
     adj : having the character of a polynomial; "a polynomial
           expression" [syn: {polynomial}]
     n : a mathematical expression that is the sum of a number of
         terms [syn: {polynomial}]