WordNet (r) 3.0 (2006):

cardholder
    n 1: a person who holds a credit card or debit card
    2: a player who holds a card or cards in a card game

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "cardholder":
   Greek, affiliate, associate, bargainer, belonger, brother,
   business agent, card-carrier, card-carrying member, charter member,
   clubber, clubman, clubwoman, committeeman, comrade, conventioneer,
   conventioner, conventionist, dues-paying member, enlistee,
   enrollee, fellow, fraternity man, guildsman, honorary member,
   initiate, insider, joiner, labor organizer, life member, member,
   negotiator, one of us, organizer, pledge, shop steward, sister,
   socius, sorority girl, sorority woman, trade unionist,
   union member, union officer, unionist