tl;dr

This is shorthand for:

"Hey guys, look at me, I have nothing to contribute to the discussion, but I'll just let you know how ignorant and stupid I am."

Commonly used on internet forums.

Poster 1: *Tries to initiate a discussion*

Poster 2: tl;dr

Person 1: Hey, here's an idea - if you have nothing to say, don't post!

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