when you want to take credit for something you already knew was done before you came up with it or claiming that someone (usually well known) stole your idea before you could get around to it.
"These people keep pre-stealing my ideas, using them, and making millions!"
"Anytime you hear someone say 'hey that's show business' keep in mind I created that"- me
"you mean a phrase i've heard all my life and I'm 15 years older than you?"- boss
"yeah, they pre-stole that from me"
"I had this really great idea for a story about two teenagers that fall in love but their families hate one another and it ended tragically but then I found Shakespeare pre-stole my idea"