The Collaborative International Dictionary of English v.0.48:

Subrogate \Sub"ro*gate\, v. t. [L. subrogatus, p. p. of
   subrogare. See Surrogate.]
   To put in the place of another; to substitute. --Barrow.
   [1913 Webster]

WordNet (r) 3.0 (2006):

subrogate
    v 1: substitute one creditor for another, as in the case where
         an insurance company sues the person who caused an accident
         for the insured