space bar definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
a bar, as at the bottom of a typewriter keyboard, pressed to leave a blank space or spaces rather than to produce a character
space bar definition by American Heritage Dictionary
A bar at the bottom of the keyboard of a typewriter or computer that when pressed down introduces a horizontal space into text, as between words.