Before the popularization of the Internet in the 1990s, Internet slang defined a luser (sometimes expanded to local user; also luzer or luzzer) as a painfully annoying, stupid, or irritating computer user. The word is a blend of "loser" and "user". Among hackers, the word luser takes on a broad meaning, referring to any normal user (in other words, not a "guru"), with the implication the person is also a loser. The term is partially interchangeable with the hacker term lamer.

The term can also signify a layman with only user account privileges, as opposed to a power user or administrator, who has knowledge of, and access to, superuser accounts; for example, an end luser who cannot be trusted with a root account for system administration. It is popular with technical support staff who have to deal with lusers as part of their job, often metaphorically employing a LART (Luser Attitude Readjustment Tool, also known as a clue-by-four, cluestick, or cluebat), meaning turning off the user's access to computer resources and the like.