What the bases mean in dating

Leman and Bell, in their book A Chicken's Guide to Talking Turkey With Your Kids About Sex, make use of it to aid parents in the discussion of puberty with their children, dividing the topics into "first base" ("Changes from the neck up"), "second base" ("Changes from the neck to the waist"), "third base" ("Changes from the waist down"), and "home plate" ("The Big 'It'").

This sequence of "running the bases" is often regarded as a script, or pattern, for young people who are experimenting with sexual relationships.

A similar example can be found in Billy Joel's song "Zanzibar" in which he compares himself to Pete Rose and sings the lines "Me, I'm trying just to get to second base and I'd steal it if she only gave the sign.

She's gonna give the go ahead, the inning isn't over yet for me." David Letterman chronicled many of these in his "Top Ten Baseball Euphemisms for Sex" — a recurring theme on the Top Ten Lists featured on the late-night talk shows he hosted before retiring in May, 2015.

But this is a joke, and probably not intended to be analyzed too closely. Although this wasn't what "House" referred to, Urban Dictionary lists fifth base as anal sex.

Talking about fifth base when there's really only four bases reminds me of the expression Up To Eleven.

"I got to second base with that girl yesterday." "I didn't think I had a chance, but I made it to third base with her last night." One of the other answers has provided a nice link to the Wikipedia entry for baseball metaphors for sex.