Some people only consider French kissing as getting to first base.
Home run Simply put, a home run is sexual intercourse Grand slam Those looking to excel at sexual baseball strive for the grand slam. Strike out A strike out is when you don't get a kiss at the end of the evening.
A grand slam is sexual intercourse with the female having an orgasm. Double header A double header consists of two rounds of intercourse in one night.
Sacrifice fly A sacrifice fly is the buddy who "takes one for the team" to ensure you end up with the girl of your choice for the evening, akin to a "wingman." Picked off When your sexual activity is interrupted by a third party (such as a parent, roommate or child), you are said to have been picked off.
There are, as the top comment on this question notes, four bases in baseball, and these have corresponding sex acts associated with them.
"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.
The sexual contact associated with each base has evolved dramatically since I was a teenager, although "home base" or "home run" has always meant intercourse, and "first base" has always meant kissing or snogging.To use the expression correctly, you get or make it to a base, per my comment: quotation, if I interpret it correctly, they had intravaginal sex twice and then she performed oral sex on him.If we say home base = fourth base, that's 4 + 4 − 3 = 5, the subtraction because he was receiving instead of giving.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.If you want to downvote me for using Urban Dictionary, that's fine. First base When you get to first base, you have been lucky enough to have been kissed.