GOOD "P.R."
'(<a href="http://www.j-archive.com/media/2008-09-30_DJ_12.wmv">Kelly of the Clue Crew bangs Jimmy of the Clue Crew on the knee.</a>)  It's the medical term for the response elicited by a tap on a particular tendon; axons quickly carry the impulse, causing the lower leg to extend'
patella reflex