from the german word "blitzkrieg", meaning lightning (a very offensive-minded war strategy developed by the germans in WW2 that advocated quick control of your enemy's territory through fast and violent military bombardment; usually combining land and air attacks).
Used in football terminology to denoted a defensive play in which many defensive players are used to try and break through the offensive line (the line protecting the quarterbacks and running backs). A Blitz usually leaves the defence vulnerable to passing plays, but it also cuts down on the time the quarterback has to throw the ball (it's main purpose is to put pressure on the quarterback or sack the quarterback).
The defence really got good penetration on that blitz.
November 24, 2003