The Collaborative International Dictionary of English v.0.48:

Reciprocation \Re*cip`ro*ca"tion\
   (r[-e]*s[i^]p"r[-o]*k[=a]"sh[u^]n), n. [L. reciprocatio: cf.
   F. r['e]ciprocation.]
   1. The act of reciprocating; interchange of acts; a mutual
      giving and returning; as, the reciprocation of kindness.
      [1913 Webster]

   2. Alternate recurrence or action; as, the reciprocation of
      the sea in the flow and ebb of tides. --Sir T. Browne.
      [1913 Webster]

WordNet (r) 3.0 (2006):

reciprocation
    n 1: the act of making or doing something in return
    2: alternating back-and-forth movement
    3: mutual interaction; the activity of reciprocating or
       exchanging (especially information) [syn: interchange,
       reciprocation, give-and-take]

Moby Thesaurus II by Grady Ward, 1.0:

71 Moby Thesaurus words for "reciprocation":
   Lissajous figure, alternation, back-and-forth, balance,
   battledore and shuttlecock, boomerang, coequality, comeback,
   coming and going, communion, community, commutation, cooperation,
   corelation, correlation, correlativism, correlativity,
   correspondence, counter, counterblast, counterblow, counterchange,
   counterstroke, cross fire, ebb and flow, equilibrium, equipollence,
   equivalence, exchange, flux and reflux, give-and-take, interchange,
   intermutation, interplay, inverse proportion, inverse ratio,
   inverse relationship, lex talionis, measure for measure,
   mutual admiration, mutual support, mutual transfer, mutuality,
   permutation, proportionality, quid pro quo, reciprocality,
   reciprocity, recoil, relativity, reply, retaliation, retort,
   return, rhythmic play, seesaw, seesawing, sine wave,
   something for something, symmetry, teeter, teeter-totter,
   teeter-tottering, teetering, tit for tat, to-and-fro, tottering,
   transposal, transposition, ups and downs, wigwag