The Collaborative International Dictionary of English v.0.48:

Retroaction \Re`tro*ac"tion\, n. [Cf. F. r['e]troaction.]
   1. Action returned, or action backward.
      [1913 Webster]

   2. Operation on something past or preceding.
      [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

42 Moby Thesaurus words for "retroaction":
   action and reaction, answer, automatic reaction,
   autonomic reaction, backset, backsliding, backward motion,
   backward step, bounceback, echo, lapse, predictable response,
   reaction, recession, recidivation, recidivism, reentry, reflection,
   reflex, reflex action, refluence, reflux, regress, regression,
   relapse, reply, respondence, response, retrocession, retroflexion,
   retrogradation, retrogression, retrusion, return, reverberation,
   revulsion, rise, rollback, setback, sternway, throwback,
   unthinking response