Definition of Iceberg lettuce

Lettuce (Lactuca sativa) is a temperate annual or biennial plant of the aster or sunflower family Asteraceae. It is most often grown as a leaf vegetable, but also sometimes for its stem and seeds. Lettuce was first cultivated by the Egyptians, who turned it from a weed whose seeds were used to make oil into a plant grown for its leaves. It then spread to the Greeks and Romans, who gave it the name "lactuca", from which the modern "lettuce" ultimately derives. By 50 AD, multiple types were described, and it appeared often in medieval writings, including several herbals. The 16th through 18th century saw the development of many varieties in Europe, and by the mid-18th century varieties were being described that can still be found in gardens. Europe and North America originally dominated the market for lettuce, but by the late 1900s the consumption of lettuce had spread throughout the world.