Hiding an erection with pillows (or any other object), while sitting down.
This term comes from a scene in Harry Potter and The Half-Blood Prince, when Mr. Weasely is talking to Hermione. Through that entire scene he is constantly holding a pillow over his crotch.
This term is not to be confused with Sporting a Weasely
, although they are similar.
Man, I totally had an erection the entire time I was talking to Sally.
Wow, what did she say about that?
Nothing, I luckily was Pulling a Weasely the whole time. She never got to see what I was hiding.