1. One who is filled with enthusiasm; one who is ardently absorbed in an interest or pursuit: a baseball enthusiast.
2. A zealot; a fanatic.

[Greek enthousiastēs, possessed person, from enthousiazein, to be inspired. See enthusiasm.]

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.