Source : Webster's Revised Unabridged Dictionary (1913)

Relative \Rel"a*tive\ (r?l"?-t?v), a. [F. relatif, L. relativus.
   See {Relate}.]
   1. Having relation or reference; referring; respecting;
      standing in connection; pertaining; as, arguments not
      relative to the subject.

            I'll have grounds More relative than this. --Shak.

   2. Arising from relation; resulting from connection with, or
      reference to, something else; not absolute.

            Every thing sustains both an absolute and a relative
            capacity: an absolute, as it is such a thing, endued
            with such a nature; and a relative, as it is a part
            of the universe, and so stands in such a relations
            to the whole.                         --South.

   3. (Gram.) Indicating or expressing relation; refering to an
      antecedent; as, a relative pronoun.

   4. (Mus.) Characterizing or pertaining to chords and keys,
      which, by reason of the identify of some of their tones,
      admit of a natural transition from one to the other.
      --Moore (Encyc. of Music).

   {Relative clause} (Gram.), a clause introduced by a relative
      pronoun.

   {Relative term}, a term which implies relation to, as
      guardian to ward, matter to servant, husband to wife. Cf.
      {Correlative}.

Source : WordNet®

relative clause
     n : a clause introduced by a relative pronoun; "`who visits
         frequently' is a relative clause in the sentence `John,
         who visits frequently, is ill'"