The Collaborative International Dictionary of English v.0.48:

React \Re*act"\ (r[=e]*[a^]kt"), v. t.
   To act or perform a second time; to do over again; to
   reenact; as, to react a play; the same scenes were reacted at
   Rome.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

React \Re*act"\ (r[-e]*[a^]kt"), v. i.
   1. To return an impulse or impression; to resist the action
      of another body by an opposite force; as, every body
      reacts on the body that impels it from its natural state.
      [1913 Webster]

   2. To act upon each other; to exercise a reciprocal or a
      reverse effect, as two or more chemical agents; to act in
      opposition.
      [1913 Webster]

WordNet (r) 3.0 (2006):

react
    v 1: show a response or a reaction to something [syn: react,
         respond]
    2: act against or in opposition to; "She reacts negatively to
       everything I say" [syn: react, oppose]
    3: undergo a chemical reaction; react with another substance
       under certain conditions; "The hydrogen and the oxygen react"

Moby Thesaurus II by Grady Ward, 1.0:

56 Moby Thesaurus words for "react":
   acknowledge, act, answer, answer back, be affected, be in tune,
   be inspired, be involved, be moved, behave, care about,
   catch the flame, catch the infection, change color,
   color with emotion, come back, come back at, dig, echo,
   empathize with, flash back, function, give acknowledgment,
   give answer, identify with, operate, perform, proceed, reciprocate,
   recur, reecho, rejoin, relate to emotionally, renovate, reply,
   respond, retaliate, retort, return, return answer,
   return for answer, reverberate, revert, riposte, say, say in reply,
   share, shoot back, snap back, sympathize with, take, take the bait,
   talk back, turn, turn back, work