From Encyclopedia Dramatica
TMI stands for "too much information". This phrase, though not used very often, (as DO NOT WANT is the current Internets standard for extreme displeasure at something) is typically used when someone admits over the Internets via IM something related to their dick or cunt that others would find unpleasant. This also applies when someone admits they view the likes of shotacon or furry porn. This abbreviation is thus a cry of pain over the mental image implanted into the brains of anyone in the conversation.
TMI can also be used intentionally, especially in relation to trolling. While effective, if used against people you know irl, the possibility of becoming more of a social outcast than you already were is possible.
Prima: I find little kids attractive LOL
Secunda: TMI! I'm calling the police!
Prima: I was only trolling!
Secunda: I DON'T FUCKING KNOW YOU
|Featured article May 26, 2011|
| Preceded by|
Frosty the Snowman
|TMI|| Succeeded by|