So this one definitely needs and update ; )

According to multiple super-reputable online sources, all of which are beyond reproach (LOLz)! These are the most common uses.

1) LOLz is meant as a sarcastic response.

2) Its secondary intent is dubious but remains insincere.

3) Lastly, some say it’s a plural form of LOL. Although this is not the main definition, it is widely used. This definition makes the least sense considering laughing out loud is of lots of laughs, LOL!

A funny side note, LOL was originally used in the pre Internet days as an abbreviation for lots of love. Following the advent of chat rooms and instant messaging this quickly mutated into lots of laughs and laugh out loud.

Other less common uses for LOLz include laugh out loud zone and laugh out loud zebras (so ridiculous).

LOL (Laugh Out Loud) but with a Z.

Funnier then just plain LOL

Laugh Out Loud (with Sarcasm)

The high increase in popularity of the infamous LOL (laughing out loud) was not enough for the teenage, trying to be cool, defying mom and dad, often emo generation. They had to come up with something even cooler and that's how LOLZ was born. Some say that Z stands for S, therefore it's the plural version of LOL. But let's analyze that thought process a bit. The plural of LOL would be translated as "laughing out loudS" or "laughingS out loud" which, for the few of us who are at least trying to be grammatically correct makes as much sense as "z" being used as a replacement for "s".
In this case, the Z could be interpreted as the initial of a completely different word. Possibilities:

1. Laughing out loud ZBANG! - this would indicate that the violent laughter has caused the person to fall and hit the ground, thus creating a loud sound;
2. Laughing out loud ZTUPID - seeing as Z is so often used as a replacement for S, it makes sense. It's also a very positive thing, when you consider that admitting you have a problem is the first step to recovery;
3. Laughing out loud ZENITH - the person doing the laughing has entered a state of astral trance...

LAUGH OUT LOUD ZILLIONS

Laughing out loud zillions of times like a moron. Skinny, tall, white males in their early twenties do this. They tend to post "LOLZ" on other people's Facebook walls while interrupting a conversation between other people and pretend they patented the phrase. Really, the term "LOLZ" is just another way of saying they are lacking down below. LOLZ

The high increase in popularity of the infamous LOL (laughing out loud) was not enough for the teenage, trying to be cool, defying mom and dad, often emo generation. They had to come up with something even cooler and that's how LOLZ was born. Some say that Z stands for S, therefore it's the plural version of LOL. But let's analyze that thought process a bit. The plural of LOL would be translated as "laughing out loudS" or "laughingS out loud" which, for the few of us who are at least trying to be grammatically correct makes as much sense as "z" being used as a replacement for "s".
In this case, the Z could be interpreted as the initial of a completely different word. Possibilities:

1. Laughing out loud ZBANG! - this would indicate that the violent laughter has caused the person to fall and hit the ground, thus creating a loud sound;
2. Laughing out loud ZTUPID - seeing as Z is so often used as a replacement for S, it makes sense. It's also a very positive thing, when you consider that admitting you have a problem is the first step to recovery;
3. Laughing out loud ZENITH - the person doing the laughing has entered a state of astral trance...

"Laughing out loud zebras."
Zebras that are laughing out loud.

LOLZ is another way to say"lol"