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)