The Collaborative International Dictionary of English v.0.48:

Covenanter \Cov"e*nant*er\ (k?v"?-n?nt-?r), n.
   1. One who makes a covenant.
      [1913 Webster]

   2. (Eccl. Hist.) One who subscribed and defended the "Solemn
      League and Covenant." See Covenant.
      [1913 Webster]