<P> Among American adolescents, baseball metaphors for sex are often used as euphemisms for the degree of physical intimacy achieved in sexual encounters or relationships . In the metaphor, first prevalent in the aftermath of World War II, sexual activities are described as if they are actions in a game of baseball . </P> <P> Among the most commonly used metaphors are the bases describing levels of physical intimacy (generally from a heterosexual perspective). Definitions vary, but the following are typical usages of the terms: </P>

Who is on first base what is on second base