What does it mean when somebody types XD?

It's a smiley that laughs sooo hard that it even close its eyes.

If you tilt your head to the left, it looks like an excited face. The X is squinted eyes, the D is a big smile.

It's an emoticon.

It's like a smiley

Instead of this-

:D

They have used this-

XD

Cross-eyed you see

it's a smiley

A smiley that laughs so hard, it squeezes its' eyes

Xavier Durden is the only person I've ever seen use it. I don't know why.

That's an emoji that got stoned with shrooms.

It's just a stupid emoticon. Eyes closed while smiling. It's like an orgasm face.

It's like a laughing hysterically "I'm dying" emoticon.

Its usually used by kids who watch anime and or play videogames

They're either a woman, or gay.