Easton's Bible Dictionary
My master, a title of dignity given by the Jews to their doctors of the law and their distinguished teachers. It is sometimes applied to Christ (Matthew 23:7, 8; Mark 9:5 (R.V.); John 1:38, 49; 3:2; 6:25, etc. ); also to John (3:26).
Noah Webster's New International Dictionary of the English Language
(n.) Master; lord; teacher; -- a Jewish title of respect or honor for a teacher or doctor of the law.