One who betrays a cause for personal advancement.The popular definition of sell out allows it to be used as an insult towards anyone in show business On the contrary , there are many bands which are considered sellouts which are not.For instance, Green Day. They are considered sell-outs because they are a punk band who was popular on MTV. Green Day never stated that they would never be on MTV, thus they are not sell-outs in that sense. They never changed their musical style for monetary reasons, thus they are are not sell-outs in the more literal sense of the word. If Fugazi were to sign up with Sony records, they would be selling out because they preach against major labels.