(CYGnus WINdows) Software that allows Unix/Linux applications to run under Windows. It is used by Unix/Linux developers to add support for Windows, to migrate applications to Windows as well as to run utilities on Windows for which there is no comparable Windows program. Originally developed by Cygnus Solutions, Cygwin is maintained by Red Hat and other vendors. The Cygwin.dll library converts the calls most Unix/Linux applications make to the operating system via the POSIX, BSD and UNIX SVR4 interfaces to Windows calls. For more information, visit www.redhat.com/services/custom/cygwin.