The Collaborative International Dictionary of English v.0.48:
Subtractive \Sub*trac"tive\, a. 1. Tending, or having power, to subtract. [1913 Webster] 2. (Math.) Having the negative sign, or sign minus. [1913 Webster]WordNet (r) 3.0 (2006):
subtractive adj 1: constituting or involving subtraction; "a subtractive correction" [ant: additive]