The Collaborative International Dictionary of English v.0.48:

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.
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            I'll have grounds
            More relative than this.              --Shak.
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   2. Arising from relation; resulting from connection with, or
      reference to, something else; not absolute.
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            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.
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   3. (Gram.) Indicating or expressing relation; refering to an
      antecedent; as, a relative pronoun.
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   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).
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   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.
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WordNet (r) 3.0 (2006):

relative clause
    n 1: a clause introduced by a relative pronoun; "`who visits
         frequently' is a relative clause in the sentence `John, who
         visits frequently, is ill'"