morphine

Short definition from Wiktionary

Noun

1. 1
   A crystalline alkaloid (4,5-epoxy-17-methyl-7,8-didehydromorphinan-3,6-diol), extracted from opium, the salts of which are soluble in water and are used as analgesics, anaesthetics and sedatives; it is one of a group of morphine alkaloids.