A take on the phrase "Pulling the wool over his/her eyes", meaning that you might as well have a whole sheep because you are lying
"You've totaly sheeped your mum, she'll never find out."
To send email from another user's account, notifying the world that this person has broken computer security policy by walking away from their computer and left it unlocked.
"Erin must have gotten sheeped! I just got an email from her saying she loved sheep and wanted to find some sailors to share them with!!"
"I'm a little teapot and I love SHEEP!"
Usually used in the game World Of Warcraft when a player or mob becomes afflicted by the Mage spell "Polymorph" turning the player into a grass eating, white, fluffy, cuddly sheep.
"Ok ok which mage didnt keep that Wolf sheeped!?"
"Man mages just keep that imba shamen sheeped the whole time!"
The experience of doing something, and then having a large group of people (the sheep) copy you.
Bob: I started spinning my pen, and next week, the whole damn class was doing it!
Brian: Dude, you were sheeped!