Source : Webster's Revised Unabridged Dictionary (1913)

Dominant \Dom"i*nant\, a. [L. dominans, -antis, p. pr. of
   dominari: cf. F. dominant. See {Dominate}.]
   Ruling; governing; prevailing; controlling; predominant; as,
   the dominant party, church, spirit, power.

         The member of a dominant race is, in his dealings with
         the subject race, seldom indeed fraudulent, . . . but
         imperious, insolent, and cruel.          --Macaulay.

   {Dominant estate} or {tenement} (Law), the estate to which a
      servitude or easement is due from another estate, the
      estate over which the servitude extends being called the
      servient estate or tenement. --Bouvier. --Wharton's Law
      Dict.

   {Dominant owner} (Law), one who owns lands on which there is
      an easement owned by another.

   Syn: Governing; ruling; controlling; prevailing; predominant;
        ascendant.

Dominant \Dom"i*nant\, n. (Mus.)
   The fifth tone of the scale; thus G is the dominant of C, A
   of D, and so on.

   {Dominant chord} (Mus.), the chord based upon the dominant.

Source : WordNet®

dominant
     adj 1: exercising influence or control; "television plays a
            dominant role in molding public opinion"; "the
            dominant partner in the marriage" [ant: {subordinate}]
     2: of genes; producing the same phenotype whether its allele is
        identical or dissimilar [ant: {recessive}]

dominant
     n : (music) the fifth note of the diatonic scale