1) Electronic device 2) Follow a 1950s TV superstar 3) Monitor cursor mover 
A trackball is a pointing device consisting of a ball held by a socket containing sensors to detect a rotation of the ball about two axes—like an upside-down mouse with an exposed protruding ball. The user rolls the ball with the thumb, fingers, or the palm of the hand to move a pointer. Compared with a mouse, a trackball has no limits on effect...
An encoder at the ACNET consoles which allows the user to change the (x,y) position of the cursor on the TV and AEOLUS screens.
(from the article `computer`) Mechanical mice and trackballs operate alike, using a rubber or rubber-coated ball that turns two shafts connected to a pair of encoders that measure ...
[n] - an electronic device consisting of a rotatable ball in a housing
noun an electronic device consisting of a rotatable ball in a housing; used to position the cursor and move images on a computer screen; `a trackball is essentially an upside-down mouse`
Input device that carries out the same function as a mouse, but remains stationary. In a trackball the ball controlling the cursor position is operated directly with the fingers
A mouse alternative that is basically an upside-down mouse. Useful for some people with mobility impairments because it isolates pointer movement from button clicking.