- The definition of a fanatic is a person who is overly excited and interested in something.
An example of fanatic is someone with a room devoted to Elvis Presley in their two-bedroom house.
fanatic definition by Webster's New World
Origin: ; from Classical Latin fanaticus, of a temple, hence enthusiastic, inspired ; from fanum, a temple: see fane
fanatic definition by American Heritage Dictionary
Origin: Latin fānāticus, inspired by orgiastic rites, pertaining to a temple, from fānum, temple; see dhēs- in Indo-European roots.