The Collaborative International Dictionary of English v.0.48:

Prow \Prow\, a. [Compar. Prower; superl. Prowest.] [OF.
   prou, preu, F. preux, fr. L. pro, prod, in prodesse to be
   useful. See Pro-, and cf. Prude.]
   Valiant; brave; gallant; courageous. [Archaic] --Tennyson.
   [1913 Webster]

         The prowest knight that ever field did fight.
                                                  --Spenser.
   [1913 Webster]