get to first base with someone
get to first base with (someone)
slang To kiss someone. The term likens sexual acts to "hits" in baseball, in which a player advances to each base on the way to "scoring"—a slang term for engaging in sexual intercourse with someone. A: "Did you get to first base with Dave last night?" B: "A lady doesn't kiss and tell!"
get to first (base) (with someone)
in. to achieve a basic or initial level of intimacy with someone, such as getting some attention or even getting kissed. I’m too shy. I just know I can’t get to first base with her.