When you engage in the art of sexual intercourse with a boy or girl that you like. It isn't a modern saying, but it's a way of explaining what you mean without actually explaining what you mean. It is ideal for classroom situations.

Micro marriging is when your partner manages your personal day-to-day tasks with you much like a Micro Manager at work.

Rumble in the Sack basically means to engage in the act of sexual intercourse. This can be with a man or woman. Rumbling in the Sack mainly means having sexual intercourse in a bed of sorts. This isn't a phrase used often as it is quite an old phrase. It is mainly used for classroom situations.