\Ni`co*la"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. (Source: Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc.)
The word Nicolaitan comes from two Greek words: nike and laios. Nike means "to conquer," "subdue," "overcome," and laos refers to a body of people, the common people. Nikos is the equivalent to nike and has been translated "victory." When combined, these two terms translate "conqueror [or subduer] of the common people."
These "conquerors of the people" were among the assembly of called-out-ones in Ephesus and Pergamos. They had influence among the saints.
(Some scholars say they were followers of Nicolas who was one of the deacons in Acts 6:5. They speculate that Nicolas went into deception and led some of the believers away from the faith. This is impossible to document.)