As a noun amateur
As an adjective undefined is
lacking a definition or value.
A lover (of) something.
* 2006 , John Hailman, Thomas Jefferson on Wine , University of Mississippi 2006, p. x:
A person attached to a particular pursuit, study, or science as to music or painting; especially one who cultivates any study or art, from taste or attachment, without pursuing it professionally.
- he conducted extensive correspondence on wines with European suppliers, employing a wine vocabulary familiar to any modern amateur of wines.
Someone who is unqualified or insufficiently skillful.
- She is an accomplished amateur woodworker.
- The entire thing was built by some amateurs with screwdrivers and plywood.
* radio amateur
Created, done, or populated by amateurs or non-professionals.
Showing a lack of professionalism, experience or talent.
- amateur sports
- Duct tape is a sure sign of amateur workmanship.
* amateur hour
* amateur night
Lacking a definition or value.
(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.
- The result of division by zero is undefined .