A pointing device consisting of a Ball housed in a socket containing sensors to detect rotation of the Ball aBout two axes - like an upside-down mouse. The user rolls the Ball with his thumB or the palm of his hand to move a cursor. Tracker Balls are common on CADworkstations for ease of use and on modern portaBle computers, where there may Be no desk space on which to use a mouse. Some clip onto the side of the keyBoard and have integral Buttons which have the same function as mouse Buttons. (1996-08-04)