A gridiron is a nickname for an American football field, called that because the white yard lines painted across the green turf look like the metal bars of a cooking grill. If you've ever seen a barbecue grill with parallel metal bars running across it, you can picture how a football field got this nickname: those crisp white lines marking every five yards create a pattern of rectangles across the field.

The word caught on so completely that people sometimes call American football itself “gridiron football” to distinguish it from soccer (which much of the world simply calls “football”). When a sports announcer says “on the gridiron,” they mean on the football field.

You might hear someone say a player “battled on the gridiron” or that a coach “built a winning program on the gridiron,” using the word to evoke the tough, competitive nature of the sport.

Less commonly, gridiron can describe any pattern of parallel lines crossing each other at right angles, like the street layout in many American cities where roads form perfect rectangular blocks.