from reddit:
Dubplates were originally acetate pressings by studios as test records to see how the track would sound before the final pressing. In Jamaican soundclash culture, the term was adopted to refer to exclusive versions of big tracks by the original artist with the lyrics changed to big up the sound system that was performing. As vinyl culture has shifted to digital, the term still stuck.
So in the context of getting Madonna to record new vocals bigging up major lazer, it's still the correct term in soundclash culture.