The Collaborative International Dictionary of English v.0.48:

Worshiper \Wor"ship*er\, n.
   One who worships; one who pays divine honors to any being or
   thing; one who adores. [Written also worshipper.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

worshipper
    n 1: a person who has religious faith [syn: believer,
         worshiper, worshipper]
    2: someone who admires too much to recognize faults [syn:
       worshiper, worshipper]

Easton's 1897 Bible Dictionary:

Worshipper
   (Gr. neocoros = temple-sweeper (Acts 19:35) of the great goddess
   Diana). This name neocoros appears on most of the extant
   Ephesian coins