watermelon, plant ( Citrullus vulgaris ) of the family Curcurbitaceae (gourd family) native to Africa and introduced to America by Africans transported as slaves. Watermelons are now extensively cultivated in the United States and are popular also in S Russia. The fleshy, juicy fruit is eaten fresh, the rind is pickled, and in Asia the seeds are eaten (the dry wild watermelon was originally domesticated for its seeds). Seedless and thin-rinded cultivated varieties have been developed, and one white-fleshed variety, the citron melon, is used like citron in preserving. Watermelons are classified in the division Magnoliophyta, class Magnoliopsida, order Violales, family Curcurbitaceae.