The Collaborative International Dictionary of English v.0.48:

Rinforzando \Rin`for*zan"do\, a. [It., fr. rinforzare to
   reenforce, strengthen.] (Mus.)
   Increasing; strengthening; -- a direction indicating a sudden
   increase of force (abbreviated rf., rfz.) Cf. Forzando, and
   Sforzando.
   [1913 Webster]