bitter melon

noun

: an herbaceous annual vine (Momordica charantia of the family Cucurbitaceae) native to the Old World tropics but widely naturalized that has oblong, warty, bitter fruits which are used as vegetables usually while green and immature

A warm weather crop, bitter melon should be seeded six inches apart after all danger of frost—grow it along a fence or trellis.—

Lynda D. Gutowski, New York Times, 24 May 1981

also : the fruit

Bitter melon darkens and becomes stronger in flavor as it matures, so one is advised to choose younger, lighter gourds. —

Nina Simonds, Gourmet, July 1980

There, as city traffic roared up North Broad Street last summer, they quietly cultivated organic bitter melon, which looks like a warty cucumber and is a mainstay of Asian cuisine … —

Virginia A. Smith, Philadelphia Inquirer, 11 Feb. 2011

Note: Both the plant and its fruit are also called balsam apple, balsam pear, bitter gourd, (India) karela, and (Philippines) ampalaya.