That the picture had been used in another thread but has the qualities of the thread you want to use it in. For example, someone posts a guy in the Armpit Appreciation thread with his hands in the air so that his pits are exposed. But the guy also has really muscular thighs. So you copy the pic and repost in the Wrap Those Thighs Around Me and Squeeze, Please thread. Generally I will also credit the person who I "stole" the pic from. Sometimes a pic could be in more than two threads.