The Collaborative International Dictionary of English v.0.48:

Nicolaitan \Ni`co*la"i*tan\ (n[i^]k`[-o]*l[=a]"[i^]*tan), n. [So
   called from Nicolas of Antioch, mentioned in Acts vi. 5.]
   (Eccl. Hist.)
   One of certain corrupt persons in the early church at
   Ephesus, who are censured in Rev. ii. 6, 15.
   [1913 Webster]