It's original definition was "Laughing out loud" (also written occasionally as "Lots of Laughs"), used as a brief acronym to denote great amusement in chat conversations.

Now, it is overused to the point where nobody laughs out loud when they say it. In fact, they probably don't even give a shit about what you just wrote. More accurately, the acronym "lol" should be redefined as "Lack of laughter."

Depending on the chatter, its definition may vary. The list of its meanings includes, but is not limited to:
1) "I have nothing worthwhile to contribute to this conversation."
2) "I'm too lazy to read what you just wrote so I'm typing something useless in hopes that you'll think I'm still paying attention."
3) "Your statement lacks even the vaguest trace of humor but I'll pretend I'm amused."
4) "This is a pointless acronym I'm sticking in my sentence just because it's become so engraved into my mind that when chatting, I MUST use the meaningless sentence-filler 'lol.'"

See: lmao, lmfao, rofl, lawl, heh, haha, lolol, and 120 for similarities.

The name 'Lol' is an abreviated form of the name 'Laurence'.

In it's day, the net abbreviation for the words "laugh out loud" and "lots of love" were both used to express true feelings.
Let's start with "Laugh Out Loud".

It is normally used, quite obviously, to imply that statement is humorous, such as;
Person 1 : I just watched (insert funny moving picture).

Person 2: Lololololololololol!!!!!11111@@@

In this example, person 2 implies that he/she is laughing at the phrase.

It's now very plain to see that Person 2 didn't even care to read the said message.

Here are the new definitions, the redifined lol.

1. I didn't care to read what you took the time to write to me, so i blurted out lol, the word that is always on the top of my mind, always to be used on message boards and all that crap.

2. I listened, but your quote lacked any humorous content. I will pretend it did to make you feel good.

3. I have nothing to say that will be of real significance to this debate/conversation, so i will pretend i know what i'm doing.

4. I really don't care.

Lots of love, my personal favourite definition, has kept it's true meaning.

The only definition...

The sender of this slang is showing that he/she loves you.
It's a sweet way, to say Lol, but sometimes i think that the sender could express it a little more, because three letters is a little cheap.

An expression used when you feel something SHOULD be funny, but don't find it funny yourself

or

An expression used to convey confusion

Originally meant "laughing out loud" but is now so overused that it now means "I find that vaguely amusing" also a filler word now when there is a puse in the conversation or the person is lost for a response, or they are too stupid or lazy to think of one.

It stands for "laughing out loud." A slight irony to this definition is that generally people don't literally laugh out loud. That's reserved for other acronyms such as, but not limited to, LMMFAO, LMAO, ROTFLMAO, etc. Lol is most commonly used as a slience breaker, a reply to a joke that is SUPPOSED to be funny but really isn't, or an answer to an uncomfortable or random statement that one couldn't think of a better response to.

A happy face that has been bred with a lol.
It may be used in moments where a normal lol is not up to standards.