noun. Mortal enemy to the public whistler. A person of dominant mentality who, upon hearing a public whistler performing, also begins to whistle. Usurper whistling is a coup attack upon the public whistler. The usurper whistler can be identified by the fact that s/he is always whistling louder and usually faster than the public whistler.
The other day I was whistling on a bus and fell victim to a usurper whistler. I was doing that part from Sitting on the Dock of a Bay and he started whistling Yankee Doodle Dandy at the top of his register. He usurp-whistled me.