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From Marshall's pitching mechanics school:
http://www.chrisoleary.com/Projects/Baseball/Pitching/ProfessionalPitche...
If you click the Ben Sheets link, this analyst goes into detail about what he thinks is Sheets' problem...his pitching hand is too far behind his body and his pitching elbow is too high at point of release, according to this analyst (and he makes a convincing comparison with Nolan Ryan).
The inverted W refers to a pitcher's pitching-side elbow being above his pitching-side shoulder at the moment when he is about to throw the ball, creating an M-like shape if drawn from non-pitching hand to non-pitching elbow to back mid-line to pitching elbow to pitching hand.