The Collaborative International Dictionary
Counteractive \Coun`ter*act"ive\ (-?kt"?v), a. Tending to counteract.
Counteractive \Coun`ter*act"ive\, n. One who, or that which, counteracts.
Wiktionary
a. That counteracts
WordNet
adj. opposing or neutralizing or mitigating an effect by contrary action [syn: antagonistic] [ant: active]
Usage examples of "counteractive".
No matter whether it was LSD, PCP, or some other substance, we didn't treat the patient with just counteractive drugs.
I mean, frequently the talking down seemed more effective than the counteractive drugs that we administered.
She began the winter with all such counteractive measures as she could employ.
And, althiough Mary's pickles had a partially counteractive effect‑since she had stirred into them the guilt of her heart, and the fear of discovery, so that, good as they tasted, they had the power of making those who ate them subject to nameless uncertainties and dreams of accusing fingers‑the diet provided by Reverend Mother filled Amina with a kind of rage, and even produced slight signs of improvement in her defeated husband.
The trouble is, the enemy only has to add a tiny amount of a counteractive agent to their gasoline, and the thing is worthless.