1The whitish tuberous root of a kind of morning glory, Ipomoea macrorhiza (I. jalapa), native to Mexico and the southern United States, which was formerly much used in medicine as a purgative; the plant itself. Also called white jalap. With distinguishing word or phrase: any of several other kinds of purgative root.
black, grey, white mechoacan, etc.: see the first element.
2US The wild potato vine, Ipomoea pandurata.
Late 16th century; earliest use found in John Frampton (fl. 1559–1581), merchant and translator. From Mechoacan (now Michoacán), the name of a state in west-central Mexico.