Wordnet 3.0
ADJECTIVE (1)
1.
opposing or neutralizing or mitigating an effect by contrary action;
The Collaborative International Dictionary of English v.0.48:
Counteractive \Coun`ter*act"ive\ (-?kt"?v), a.
Tending to counteract.
[1913 Webster]
The Collaborative International Dictionary of English v.0.48:
Counteractive \Coun`ter*act"ive\, n.
One who, or that which, counteracts.
[1913 Webster]
WordNet (r) 3.0 (2006):
counteractive
adj 1: opposing or neutralizing or mitigating an effect by
contrary action