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"

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "correlate":
   ally, alter ego, analogon, analogue, apply, associate, bind,
   bracket, brother, close copy, close match, cognate, companion,
   complement, congenator, congener, connect, coordinate, corelate,
   correlative, correspondent, counterpart, couple, draw a parallel,
   each other, equate, equivalent, fellow, identify, image,
   interrelate, kindred spirit, like, likeness, link, match, mate,
   near duplicate, obverse, one another, parallel, parallelize,
   pendant, picture, reciprocal, reciprocatist, reciprocator, relate,
   relativize, second self, similitude, simulacrum, sister, soul mate,
   such, suchlike, tally, the like of, the likes of, tie, twin, wed