flag·el·lant 
(flăjə-lənt, flə-jĕlənt)
(flăjə-lənt, flə-jĕlənt)n.
1. One who whips, especially one who scourges oneself for religious discipline or public penance.
2. One who seeks sexual gratification in beating or being beaten by another person.
[Latin flagellāns, flagellant-, from present participle of flagellāre, to whip; see FLAGELLATE.]
flagel·lant adj.
flagel·lant·ism n.