Source : Webster's Revised Unabridged Dictionary (1913)

Counterirritant \Coun"ter*ir`ri*tant\ (-?r"r?-tant), n.,
Counterirritation \Coun"ter*ir`ri*ta"tion\, n.
   See {Counter irritant}, etc., under {Counter}, a.

Source : WordNet®

counterirritant
     n : a medicine applied locally to produce superficial
         inflammation in order to reduce deeper inflammation