Better Half and I tonight watched (on DVD) the last three episodes (ever! Aiiiigggghhh!) of Arrested Development. Luckily for BH, he had the remote control and a native speaker of American English sitting next to him--and he knows how to use them. This time he used them to ask: "What is second base?" Of course, this is a baseball term, and also a metaphor for sexual activities, but there's some dispute/lack of clarity about which bases stand for which activities. The (probably most) standard progression is:
touching above the waist
touching below the waist
Back in my more innocent days, before all the facts of life had presented themselves to me, my friends and I believed that first base was holding hands and second base was kissing and third base was kissing with tongues--and I have no idea what we thought a home run was. For others, second is touching outside the clothes, and third is getting inside the clothes. I'm sure there are all sorts of other permutations these days. Wikipedia has an article that includes many other baseball metaphors about sex, some of which probably have little currency outside the Wikipedia article.
Now, go forth and enjoy the final (and truncated) (BrE) series/(AmE) season of Arrested Development! (Though it seems to have been bounced off the air by snooker this week, thus postponing its tragic end.)