"Stop talking for a second." From the ASCII DC3 or XOFF character (the pronunciation /X-of/ is therefore also used). Control-S differs from {control-O} in that the person is asked to stop talking (perhaps because you are on the phone) but will be allowed to continue when you're ready to listen to him -- as opposed to control-O, which has more of the meaning of "Shut up." Considered silly.
[glossary]
[Reference(s) to this entry by made by: {control-O}{control-Q}{XOFF}]