awknowledgement of someones comment or joke, but indicating it wasn't funny.

A stupid person; it refers to the lack of surface area on an individual's brain. The general thought is that the more surface area (wrinkles, creases, etc.) a brain has, the smarter the person is. Conversely, a person with a smooth brain (no wrinkles) has less surface area and would therefore be stupid.

it was funny but im to lazy to type.

what lil wayne always says in the middle of his songs

When someone tells you a joke/story that's not funny.

some times used to show amusement.
sometimes used to show that what the person is saying, doing, trying to do,or asking is complete unresonable on your standards.

Like lol, it is meant to convey a laugh in texting and instant messaging, but unlike lol, you must actually have laughed before typing it. It also implies more confident laughter.

Basically it's a way to say lol, without having to say lol. It's great.