1. To masturbate on webcam (so called because Leslie Grantham was caught in his Eastenders dressing room doing just that)
2. To generally be a sexual deviant in an unpleasant manner (we can thank both John Leslie the British TV presenter, accused of some nastiness to one Ulrika Jonsson, and the aforementioned Leslie Grantham for this usage)
I was idly browsing some webcam chatrooms today when, much to my disgust (though not surprise), I caught my friend Chris Doing A Leslie from his pad in France.