When a well-known thot claims another girl is a thot even though they probablyaren't.
Kirstyn-"OMG, did you seeLauren? She looks like such a thot."
Me-"Shut the fuck up Kirstyn, get that thot-ception outta here. You the biggest whore in the school."
When a person on twitter, usually female, is not as attractive in person as they seem to be in their avi/twitter pictures. Usually due to filters/excessive makeup.
"Dude, remember that chick whose DM's I dove into last week after she posted that cleavage-heavyselfie?"
"Yeah man. Looks great in her avi, why?"
"I ran into her last night. Biggest case of twitception ever. She was a COW."