The Collaborative International Dictionary of English v.0.48:
Indorser \In*dors"er\, Indorsor \In*dors"or\, n. The person who indorses. [Written also endorser.] [1913 Webster]WordNet (r) 3.0 (2006):
indorser n 1: someone who expresses strong approval [syn: subscriber, endorser, indorser, ratifier] 2: a person who transfers his ownership interest in something by signing a check or negotiable security [syn: endorser, indorser]