What does the phrase "laugh it up" mean?

Question

I have come across it in the first episode of the sixth season of Friends. Here is the context:

Rachel: Well, I guess we just find a divorce lawyer? (Looks at Ross.)

Chandler: Well, I think, I think, Ross already has one. Now, this one’s free, right? Because you paid for the first two, so the third one’s free.

Ross: Laugh it up, but the joke’s on you. Because we don’t need to get divorced, okay? We we’re just gonna get an annulment.

I couldn't find any dictionary that gave the definition of laught it up. Is this some kind of non-standard American phrase? Could you tell me what it means and what is the synonymous phrase of it?

Answer 1

When we follow a verb with it up in the sense used in laugh it up, it generally indicates that we are talking about doing something excessively, or putting on an act.

ham it up:

[Merriam-Webster]
informal
: to act or behave in an exaggerated or playful way
// She likes to ham it up for the camera.

camp it up:

[Merriam-Webster]
informal
: to act with exaggerated speech or gestures
// He really camped it up on stage.

live it up:

[Merriam-Webster, from live]
: to live with gusto and usually fast and loose
// lived it up with wine and song
— Newsweek

Laugh it up, in terms of its descriptive sense, has a similar exaggeration. It suggests a person laughing long and hard because they find something hilarious.

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When used as an imperative (somebody being told to laugh it up), it's being used metaphorically and sarcastically.

Its meaning is similar to the following:

Enjoy it while you can, because it won't last for long.
(And soon you won't be laughing about it, because you'll see it's not actually funny, so get it out of your system now.)

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I find it unusual that there seems to be no direct reference to this particular phrase, even though I'd say it has wide use and is commonly understood.

Answer 2

To “laugh it up” loosely means to “share a laugh with a group of people”. In this context Ross’s first sentence could be interpreted as “you can continue joking about it but you don’t know all the details”.