Abbreviation for Paul Is Dead: a phenomenon whereby people search for hidden clues indicating that--on
November 9, 1966--Paul McCartney met a tragic end and was secretly replaced by a double. The rumor was borne in 1969 and quickly debunked; but has resurfaced recently with
YouTube videos purporting to have evidence that he died.
The clues in question are usually photographs of the Beatles with only Paul holding a black prop, or some lyric that sounds like, "Paul is dead,"--or something to that effect--when it's played backwards.