Source : Webster's Revised Unabridged Dictionary (1913)

Indorser \In*dors"er\, Indorsor \In*dors"or\, n.
   The person who indorses. [Written also {endorser}.]

Source : WordNet®

indorser
     n 1: someone who expresses strong approval [syn: {subscriber}, {endorser},
           {ratifier}]
     2: a person who transfers his ownership interest in something
        by signing a check or negotiable security [syn: {endorser}]