: any of a genus (Hypericum of the family Guttiferae, the Saint-John's-wort family) of herbs and shrubs with showy yellow flowers; especially: one (H. perforatum) of dry soil, roadsides, pastures, and ranges that contains a photodynamic pigment causing dermatitis due to photosensitization in sheep, cattle, horses, and goats when ingested—see hypericism
usuallySaint John's wort: the dried aerial parts of a Saint-John's-wort (Hypericum perforatum) that are held to relieve depression and are used in herbal remedies and dietary supplements
Biographical Note for SAINT–JOHN'S–WORT
John the Bap·tist\-ˈbap-təst\ , Saint(flourished 1st century AD), Jewish prophet. John lived approximately at the same time as Jesus Christ. He is considered by Christians the last of the Jewish prophets and the forerunner of Christ. John preached the imminence of God's Final Judgment and the Messiah. He baptized his followers as a token of repentance, and Jesus himself received his rite of baptism. He was executed by Herod Antipas for publicly opposing the latter's marriage to Herodias. Saint-John's-wort derives its name from the fact that it was traditionally gathered on the eve of his feast day (June 24) and used to ward off evil spirits and as a medicinal herb.