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.
Person 1: Hi
Person 2: Hey
Person 1: umm..
Person 2: uh.....
Person 1: lol
Person 1: I like to pick my nose and then massage the boogers on my anal orifice
Person 2: lol
Person 1: I got fired from my job today, got dumped, contracted HIV, lost an eye, got caught masturbating in the elementary school parking lot then shot the cop who tried to arrest me
Person 2: lol
It's the shortened version of the word "mami." Used in refrence to a female, generally one held in higher esteem than the average chickenhead.
Can also be used as a nickname for one's mother.
Female: Damn boy you fine as hell!
Male: Thanx ma...
When one puts on the illusion of having legitimate activities to do when in reality they're just trying to avoid you for some unexplicable reason. Uses such excuses as, "I can't talk now, I gotta study for my 5000954543098534 tests" or "Sorry but I can't chill with you anymore today because I have 4343290^7 appointments to go to." Extremely annoying, not very clever and the only person that these people fool are themselves.
Me: *dials number* Hey baby!
Boyfriend: Hey I gotta run because I have to go clean the house all day! *click*
Me: Damn it, hes artificially busy again, must be with that bitch Shaneese