Besides its literal meaning (related to or contained in the Bible), “Biblical” is used as an intensifier, especially in the phrase “of biblical proportions”. For example, “a flood, plague, famine, etc., of biblical proportions” (obviously, this is not to be taken literally).

“Biblically” is often used in reference to the verb “to know”, which is used in the Bible as a euphemism for having sexual relations. So if you say you know someone, and your friend asks you if you mean that “biblically”, you can draw your own conclusions….

Hello.

Here in Brazil the word "biblically" is more common in a conversation between people who follow some Christian denomination.

Example: someone is gossiping, and another one says: "What are you doing?! Think biblically!". Although gossip is a "normal" thing, the Bible says that gossip is a bad/wrong thing.

Here in Brazil it is common to hear lawyers using the word "juridically" and "legally".

Example: a pedestrian is crossing the street, and another pedestrian says: "What are you doing?! This is juridically wrong!". Although crossing the street is a "normal" thing, there are laws that specify the correct way to do that, for example, you have to walk at a crosswalk.

The same pick-up line exists in Arabic, it never works.

Phil, I realised that there is a parallel in Russian to that biblical sexual usage.

In biblical Russian we use resultative form of "to know", which means "to learn", "get to know", an act of transition form not knowing to knowing. Познать.

There is another verb (from a related root знак 'sign') - познакомиться. Means 'become acquinted, familiarize yourself with someone or something', 'get to know'.

And it is used often in the context of young people of opposite gender. A girl saying that she 'got to know a young man' implies that she's interested, a young man saying that he wants to get to know a girl in a bus means she is pretty. "I got to know Mary" or "got to know a person..." don't imply anything like that.

And the dumbest Russian pick-up line ever is "girl, may I get to know you?" "no". The answer "no" is almost a reflex, girls first say "no" then think. Which makes sense, because it's dumb. It is half-way towards developing a new meaning. And it makes me feel a bit weird, because it's whole new notion. (maybe that's why such a reflectory reaction). I mean, normally to get aquainted with someone I just say "hello, I'm Kostya" and now we are aquainted. You can't say you know someone, but don't know her yet, because you're not sure if she is ready to know you, but you know each other anyway. Knowign is not voluntary. But in the pick-up line it comes with "may", it is something the girl may or may not agree upon.

For U.S. usage, Phil has it right.