WordNet (r) 3.0 (2006):

empathize
    v 1: be understanding of; "You don't need to explain--I
         understand!" [syn: sympathize, sympathise, empathize,
         empathise, understand]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "empathize":
   accord, agree, agree with, be affected, be in tune, be inspired,
   be involved, be moved, care about, catch the flame,
   catch the infection, change color, chime in with,
   color with emotion, correspond, cotton to, dig, echo,
   empathize with, fall in with, get along, get along with,
   get on with, harmonize, harmonize with, identify with, interchange,
   react, reciprocate, relate to emotionally, respond, respond to,
   share, sing in chorus, sympathize, sympathize with,
   understand one another