The Collaborative International Dictionary of English v.0.48:
Fanatical \Fa*nat"ic*al\, a. Characteristic of, or relating to, fanaticism; fanatic. -Fa*nat"ic*al*ly, adv. -- Fa*nat"ic*al*ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
fanatical adj 1: marked by excessive enthusiasm for and intense devotion to a cause or idea; "rabid isolationist" [syn: fanatic, fanatical, overzealous, rabid]