verb: When you hold a girls legs apart and begin to vigorously eat her out until said female orgasms all over your face leaving it covered in in the sweetvagina sauce, it is called this do to the resemblence to eating one of Gods greatest inventions, the watermelon.
Verb; used to describe an African-American or extremely tan person whose bodies produce excess amounts of Melonin, the chemical which allows skin on the body to tan. 'Watermelonin' refers to the racial stereotype of African-American's having an overt fondness for Watermelons, thus anyone with an excessively dark complexion is said to have Matermelonin.