To press and release a button on a moUSe or other pointing device. This generates an event, also specifying the screen position, which is processed by the window manager or application program. On a moUSe with more than one button, the unqualified term USually implies pressing the left-most button (with the right index finger), other buttons would be qualified, e.g. "right-click". Keyboard modifiers may also be USed, e.g. "shift-click", meaning to hold down the shift key on the keyboard while clicking the moUSe button. If the moUSe moves while the button is pressed then this is a drag. (1995-03-14)