(1) A network operating system from IBM that runs as a server application under OS/2 and supports DOS, Windows and OS/2 clients. Originally based on LAN Manager when OS/2 was jointly developed by IBM and Microsoft, starting with LAN Server 3.0, it runs only under IBM's version of OS/2.

LAN Server provides disk mirroring, CID capability and Network Transport Services/2 (NTS/2) for concurrent access to NetWare servers. Options are LAN Server for the Macintosh for Mac client access and System Performance/2 (SP/2), a series of network management utilities.

(2) (LAN server) Generically, a file server in a network.