The Collaborative International Dictionary of English v.0.48:

Schoolmaster \School"mas`ter\, n.
   1. The man who presides over and teaches a school; a male
      teacher of a school.
      [1913 Webster]

            Let the soldier be abroad if he will; he can do
            nothing in this age. There is another personage
            abroad, -- a person less imposing, -- in the eyes of
            some, perhaps, insignificant. The schoolmaster is
            abroad; and I trust to him, armed with his primer,
            against the soldier in full military array.
                                                  --Brougham.
      [1913 Webster]

   2. One who, or that which, disciplines and directs.
      [1913 Webster]

            The law was our schoolmaster, to bring us unto
            Christ.                               --Gal. iii.
                                                  24.
      [1913 Webster]

WordNet (r) 3.0 (2006):

schoolmaster
    n 1: presiding officer of a school [syn: headmaster,
         schoolmaster, master]
    2: any person (or institution) who acts as an educator
    3: food fish of warm Caribbean and Atlantic waters [syn:
       schoolmaster, Lutjanus apodus]