A penis is the primary sexual organ that male animals use to inseminate sexually receptive mates (usually females and hermaphrodites) during copulation.
Penis is derived from the Latin word for tail, popping up in Cicero's ad Familiares. The Greek translation of phallus is swell, and the word later came to describe items of penile nature in Latin. English use of the words vulva and vagina come from identical terms in Latin meaning.
Meaning: "penis," earlier "tail," from PIE *pes- "penis" (source also of Sanskrit pasas-, Greek peos, posthe "penis," probably also See more definitions.