Source : Webster's Revised Unabridged Dictionary (1913)

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