(1) Software that provides access to all required applications. The Web browser is widely hailed as "the" universal client because all Web browsers available for PC, Mac and Linux desktops are capable of reaching every site on the Web.
(2) An e-mail client (mail program) that can access multiple messaging systems.
(3) A computer or terminal that provides access to all required applications. In this regard, a desktop or laptop is a universal client compared to the hardwired terminals of the past.