To have (or have had) sexual relations with someone. In certain versions of the Bible, "to know someone" means to have sexual relations with them, as in Genesis 4:1: "And Adam knew Eve his wife, and she conceived and bore Cain." Bob: "You know Samantha quite well, right?" Dave: "Well, I don't know her in the biblical sense, if that's what you're asking." John is looking very well these days. I'd like to get to know him in the biblical sense, if you know what I mean.