The Collaborative International Dictionary of English v.0.48:

Reverter \Re*vert"er\, n.
   1. One who, or that which, reverts.
      [1913 Webster]

   2. (Law) Reversion. --Burrill.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

REVERTER. Reversion. A formedon in reverter is a writ which was a proper
remedy when the donee in tail or issue died without issue and a stranger
abated: or they who were seised by force of the entail discontinued the
same. Bac. Ab. Formedon, A 3.