Either corner of the field formed by the sideline and the defending team's goal line. The ball may be deliberately punted out of bounds in this area, thus forcing the receiving team to play very close to its goal line.
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Coffin corner (aviation) — The coffin corner (or Q corner) is the altitude at or near which a fast fixed wing aircraft s stall speed is equal to the critical Mach number, at a given gross weight and G force loading. At this altitude the airplane becomes nearly impossible… … Wikipedia