An act of masturbation on a plane under a blanket while watching a film.
First happened while a guy was watching the Bond flick 'Live & Let Die', and was caught having a cheeky one under his blanket over Solitaire (Jane Seymour). Hence 'A Solitaire Shuffle'.
'Hey Mikael, what are you doing under that blanket? Are you having 'A Solitaire Shuffle'?'