The Collaborative International Dictionary of English v.0.48:

Correlate \Cor`re*late"\ (k[o^]r`r[-e]*l[=a]t" or
   k[o^]r"r[-e]*l[=a]t`), v. i. [imp. & p. p. Correlated; p.
   pr. & vb. n. Correlating.] [Pref. cor- + relate.]
   To have reciprocal or mutual relations; to be mutually
   related.
   [1913 Webster]

         Doctrine and worship correlate as theory and practice.
                                                  --Tylor.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Correlate \Cor`re*late"\, v. t.
   To put in relation with each other; to connect together by
   the disclosure of a mutual relation; as, to correlate natural
   phenomena. --Darwin.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Correlate \Cor"re*late\ (k?r"r?-l?t), n.
   One who, or that which, stands in a reciprocal relation to
   something else, as father to son; a correlative. --South.
   [1913 Webster]

WordNet (r) 3.0 (2006):

correlate
    adj 1: mutually related [syn: correlative, correlate,
           correlated]
    n 1: either of two or more related or complementary variables
         [syn: correlate, correlative]
    v 1: to bear a reciprocal or mutual relation; "Do these facts
         correlate?"
    2: bring into a mutual, complementary, or reciprocal relation;
       "I cannot correlate these two pieces of information"