LULZ is an abbreviated version of LOL("Laughing Out Loud"), mostly used by so called computer hackers. LULZ was brought into popularity by the popular computer hacking group: "Anonymous".
the funny things i say with my friends. means LOL. hehe. and is totally random. used to confuse people and make it look like you have a secret language.
Luke: hi
Me: heyy
Luke: whats up?
Me: nothing much.
Luke: cool
Me: lulz
Luke: what does 'lulz' mean
Me: your not cool enough to know, even if you are Luke. hehe lulz
Luke: now im offended. lulz
Me: No. just no luke. no
Lulz is derived from LOL, which stands for Laughing Out Loud. It is a form of Internet slang with orgins residing in Leet talk. In my experience, the connotation is more sarcastic, ridiculing the use of any form of the acronym or the joke being made. In some circles, it is also considered a pun on the word Lull, reinforcing the sarcastic connotation.