A function/shortcut used in the Windows operating system. Pressing the Windows Key and the letter 'D' simultaneously will minimise any folder/program/window that is on the screen at the time.
Due to this function's popularity with risk-taking pornography fanatics (to quickly hide evidence of unscrupulous activity), it can be humorous to shout "WINDOWS KEY D" while entering a friend's room when you know they are using a computer.
Bill swifty entered Scott's room while shouting "WINDOWS KEY D" (windows key + d) to find Scott abusing himself with the GIF section of 4chan.org displayed on his monitor.
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.