http://www.fifa.com/mm/document/affederation/generic/01/66/5...
This definition applies to the FA per it's constitution and bylaws.
"All Clubs and Aiffliated Associations shall play and/or administer football in conformity with these Rules and also: (a) The Laws of the Game (as defifned in the Articles); and (b) the statutes and regulations of FIFA and UEFA which are in force from time to time." [THE RULES OF THE FOOTBALL ASSOCIATION LIMITED, page 1]
http://www.thefa.com/~/media/Files/TheFAPortal/governance-do...
Here is a list of references to "association football" on the FA's Website: https://www.google.com/search?q=site%3Athefa.com+%22associat...
"Beach Soccer" is of course relevant because that's the name of the game sanctioned by FIFA.