Source : Webster's Revised Unabridged Dictionary (1913)

Hairsplitter \Hair"split`ter\, n.
   One who makes excessively nice or needless distinctions in
   reasoning; one who quibbles. ``The caviling hairsplitter.''
   --De Quincey.

Source : WordNet®

hairsplitter
     n : a disputant who makes unreasonably fine distinctions