Source : Webster's Revised Unabridged Dictionary (1913)

Subtractive \Sub*trac"tive\, a.
   1. Tending, or having power, to subtract.

   2. (Math.) Having the negative sign, or sign minus.

Source : WordNet®

subtractive
     adj : constituting or involving subtraction; "a subtractive
           correction" [ant: {additive}]