Swedish bitpop group from Norrköping, Sweden. Consists of six swedes and their analogue synthesizers. The band's name is a literal translation in Swedish of "Fight Club".
Can also be used as a verb, in which case it means to cause several orgasms in ones ears.
Also known as SMK
Swede1: Did you go see slagsmalsklubben last night?
Swede2: What did you say? I can't hear anything because slagsmalsklubben caused several orgasms in my ears last night.