Source : Free On-Line Dictionary of Computing

Media Access Control
     
         (MAC) The lower sublayer of the {OSI} {data link
        layer}.  The interface between a {node}'s {Logical Link
        Control} and the network's {physical layer}.  The MAC differs
        for various physical media.
     
        See also {MAC Address}, {Ethernet}, {token ring}.
     
        [What does it do?  Examples?  "Media" or "Medium"?]
     
        (1996-01-29)