n. A person who is interested in a subject or an activity as a hobby
The Century Dictionary and Cyclopedia
n. One who rides a hobby; one who is devoted in an enthusiastic and one-sided manner to a particular principle, pursuit, method, or “fad.”
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
n. a person who pursues an activity in their spare time for pleasure
Word Usage
"For instance, Tom Bethel, in his review of the film, says that you are a biologist (as opposed to a hobbyist, which is what I've heard most often you describing yourself as) and that you conceal your identity "for obvious reasons.""