"... out on the slippery dance floor ... maybe 600 people were one huge pulsing sweating human mass, an orgiastic being ready to split the seams of its tight-fitting garment: the disco. 'They're really moving nicely now. They're really into it!' screamed Bobby 'Bobby DJ' Guttadaro above the music ..." Richard Szathmary and Lucian K. Truscott IV, The Village Voice, July 21, 1975
In a calmer moment, Merriam-Webster defined disco as "popular dance music characterized by hypnotic rhythm, repetitive lyrics, and electronically produced sounds."
The word itself described both the music and the kind of dance club where people enjoyed that music. It comes from discotheque, a French word that originally referred to a collection of phonograph records.
Despite its success throughout most of the decade (and the massively popular Saturday Night Fever soundtrack of 1977), by late 1979 Billboard's Top Ten was disco-free.