BIT, a piece of anything. The word is used in various special senses, all derivable from its origin ("to bite"), either literally or metaphorically. The most common of these are (1) its use as the name of various tools; e.g., centre-bit ; (2) a horse's "bit," or the metal mouthpiece of the bridle; (3) a small sum of money of varying value; e.g., threepenny bit. In the United States, espe cially the western part, the term "two bits" is commonly used for twenty-five cents.