To know someone in the biblical sense means that you have had sexual intercourse with him or her. It is a reference to the meaning of "know" in the Bible.
Man 1: What do you mean by "know in the biblical sense"?
Man 2: I've slept with her. We dated last year.
Man 2: I've slept with her. We dated last year.
by A1988 December 12, 2012
Get the know in the biblical sensemug.