Top definition
When somebody who always tries to maintain a high level of coolness / hipsterness on Facebook is tagged in a ridiculous image or status by an old friend or family member, which makes them ashamed and destroys their Facebook 'image'.

This also happens when one of their family members comments on one of their photos with something retarded.
Have you seen how Poppy's older sister has commented on literally every one of her photos? What an Uncoolness Leak, man.
by AgentB August 25, 2011
Get the mug
Get a Uncoolness Leak mug for your Aunt Rihanna.