Corn flour is a finely ground powder made from dried corn kernels, used as the base for tortillas, tamales, and cornbread depending on how coarsely it is milled. In American usage it overlaps with cornmeal and masa harina (nixtamalized corn flour); in British usage, however, 'cornflour' refers to cornstarch, a pure corn starch used as a thickener, which is a different product from the flour described here. Corn flour has a mildly sweet, nutty flavor and is a foundational ingredient in Mexican, Central American, and Southern U.S. cooking, as well as in Italian polenta and Indian and African flatbreads.
For the regional use of the one-word label, see cornflour. In many British recipes it means cornstarch rather than this whole-corn flour.