I ran across this in an article on the 1955 Le Mans 24 hour race (the worst
motor racing accident in the history of the sport) and had never heard of
them.  But what a great word!

Those of you who are Ducati fans will know what they are:
http://en.wikipedia.org/wiki/Desmodromic_valve

Drop this term at your next "Cars and Coffee" meet up and impress your
friends (maybe, or maybe not)!

Stuart