a club enthusiastically devoted to a movie star or other celebrity or to a sports team.
Baseball Slang True Fans Should KnowThe game dates back a long way (the first pro team started in 1869—the Cincinnati Reds) so there’s a long history here.
Origin of fan club
First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for fan club
an organized group of admirers of a particular pop singer, film star, etc
be a member of someone's fan club informal to approve of someone strongly
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012