(Usenet) Said of a person whose account on a computer has been removed, especially for cause rather than through normal attrition. "He got disusered when they found out he'd been cracking through the school's Internet access." The verb "disuser" is less common. Both usages probably derive from the DISUSER account status flag on VMS; setting it disables the account.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)