listener, attender, public, entertainer, eavesdropper, attendee, adviser, attendant, hearer, actor, witness, critic, confessor, meeter, examiner, patron, spectator, tender.
In fact, Sylvia had unconsciously taken his place as actor in the game while he remained spectator, and, as it turned out, an auditor
of a conversation not intended for his ears.
In a quarter of an hour his auditor
was acquainted with the facts of a highly unpleasant case, but exhibited no surprise when she heard what her secretary had to do with the matter.
Having finished my task I had gathered my horse to fall back to my place at the rear, when my distinguished auditor
said, " I'm acquainted with your mother, you know."