A dark-brown, slightly firmer variation of the everyday cultivated white mushroom. Cremini mushrooms have a slightly fuller flavor than their paler relatives. They have a smooth, rounded cap that ranges in size from 1/2 to 2 inches in diameter. The portobello mushroom is simply the fully matured form of this mushroom. The cremino is also referred to as common brown mushroom and Roman mushroom. See also mushroom.