Seitan is a meat substitute made from cooked wheat gluten, produced by kneading wheat flour dough in water to wash away the starch and leave the elastic gluten behind, which is then seasoned, shaped, and cooked.
The technique dates to around the 6th century in China, where Buddhist monks used wheat gluten to make meat-like dishes within a vegetarian diet. The name "seitan" itself is a 20th-century Japanese coinage, popularized in the West in the 1960s through the macrobiotic movement, distinct from the older Chinese dish (sometimes called kao fu) it descends from.
Seitan takes on the flavor of whatever it's cooked with: in East Asian dishes it's typically seasoned with soy sauce, garlic, and ginger in stir-fries, soups, and braised dishes; in Western vegetarian and vegan cooking it stands in for meat in burgers, "chicken" nuggets, and "steak" sandwiches. Its texture ranges from firm and chewy to tender, and its flavor is savory, slightly nutty, and umami-rich.