The coffin corner refers to the corner of the playing field in American football just in front of the end zone, from about the 5-yard line to the goal line, where the punter attempts to place their kick as to minimize the opposing team's field position.
A perfect coffin corner kick is one that goes out of bounds just before either orange pylon located in the front of the end zone.
If the ball goes out of bounds too far upfield, the receiving team will usually have more options on offense, such as being able to drop back for a pass without fear of possibly giving up a safety.
More often than not, a kicker's attempt to land the ball accurately within the coffin corner fails, as the amount of skill required to angle a kick inside such a small area is extraordinary.
[2] In recent years, as punters have become more adept at kicking the ball so as to not have it bounce forward after landing, punting teams have increasingly eschewed coffin corner punts in favor of kicking inbounds and downing the ball before it reaches the end zone.