amateur

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One who engages in an art, science, study, or athletic activity as a pastime rather than as a profession.
• noun Sports An athlete who has never accepted money, or who accepts money under restrictions specified by a regulatory body, for participating in a competition.
• noun One lacking the skill of a professional, as in an art.
• adjective Of or performed by an amateur.
• adjective Made up of amateurs.
• adjective Not professional; unskillful.

from The Century Dictionary.

• noun One who admires; an admirer; a lover.
• noun One who has an especial love for any art, study, or pursuit, but does not practise it.
• noun Most commonly, one who cultivates any study or art from taste or attachment, without pursuing it professionally or with a view to gain: often used of one who pursues a study or an art in a desultory, unskilful, or non-professional way.
• noun Specifically, in sporting and athletics, an athlete who has never competed in a match open to all comers, or for a stake, or for public money, or for gate-money, or under a false name, or with a professional for a prize, and has never taught or pursued athletic exercises as a means of support.
• Pertaining to or having the character of an amateur: as, amateur work; an amateur pianist.

from the GNU version of the Collaborative International Dictionary of English.

• noun A person attached to a particular pursuit, study, or science as to music or painting; esp. one who cultivates any study or art, from taste or attachment, without pursuing it professionally.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A lover of something.
• noun 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.
• noun Someone who is unqualified or insufficiently skillful.
• adjective Non-professional.
• adjective Created, done, or populated by amateurs or non-professionals.
• adjective Showing a lack of professionalism, experience or talent.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an athlete who does not play for pay
• adjective engaged in as a pastime
• noun someone who pursues a study or sport as a pastime
• adjective lacking professional skill or expertise