Source : Webster's Revised Unabridged Dictionary (1913)

Contrayerva \Con`tra*yer"va\, n. [Sp. contrayerba, literally, a
   counter herb, hence, an antidote for poison, fr. l. contra +
   herba herb.] (Bot.)
   A species of {Dorstenia} ({D. Contrayerva}), a South American
   plant, the aromatic root of which is sometimes used in
   medicine as a gentle stimulant and tonic.