What is the definition of rock n roll?

Awesome but loud and noisy modern music

+++ More specifically it is the style given that name when it was invented in the 1950s, mainly from 12-bar blues with jazz and vague C&W influences.

It was notable for very simple lyrics backed by driving, syncopated drum rhythms and the first widespread use of the electric guitar as a lead rather than mainly rhythm instrument.

By later standards it was not ever so loud - probably not much louder than a swing band at full throttle - because the amplifiers of the time were of modest power.

It caught on as it did because popular music had stagnated, thanks at least partly to the record industry and commercial radio's advertising-agency clients; and here was something new and excitingly rebellious for youngsters who previously had nothing cultural or artistic of their "own".