Masturbation refers to sexual stimulation, especially of one's own genitals (self masturbation), often to the point of orgasm.[http://www.webmd.com/sex-relationships/guide/masturbation-guide Your Guide to Masturbation ] The stimulation can be performed manually, by other types of bodily contact (short of sexual intercourse), by use of objects or tools, or by some combination of these methods. Masturbation is a common form of autoeroticism, and the two words are often used as synonyms, although masturbation with a partner (mutual masturbation) is also common. Animal masturbation has been observed in many species, both in the wild and in captivity. Bruce Bagemihl: Biological Exuberance: Animal Homosexuality and Natural Diversity. St. Martin's Press, 1999. ISBN 0-312-19239-8
