Source : Free On-Line Dictionary of Computing

horizontal scan rate
     
         (HSR) The measure of how many {scan lines} of
        {pixels} a {monitor} can display in one second, expressed in
        kHz (generally somewhere between 20 and 100 kHz).
     
        The HSR is controlled by the horizontal sync signal generated
        by the {video controller}, but is limited by the speed with
        which the monitor can scan the electron beam horizontally
        across the screen and then return it to the beginning of the
        next line.
     
        (1996-02-09)