Trackball
ahd-5
noun.
A ball mounted in a stationary housing and rotated to control a pointer on a computer screen.
Wiktionary, Creative Commons Attribution/Share-Alike License
noun.
A
pointing
device
consisting of a
ball
housed in a
socket
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
noun.
an electronic device consisting of a rotatable ball in a housing; used to position the cursor and move images on a computer screen