Rock
Unless you've been living your whole life on a Nepalese mountaintop, you probably have a pretty good idea what "rock" is. You know that today the term is used to describe a considerably wider range of music than it was in, say 1955, when Bill Haley and the Comets topped the charts with "Rock Around the Clock," or even ?63, when the Beatles did the same with their first single, "Please Please Me."
After that early R&B/blues-based rock model inspired thousands of artists, the genre began to expand and subdivide endlessly. Over the course of a few short decades, genres as diverse as garage, psych, surf, folk-rock, glam, prog, punk, New Wave, No Wave, hard rock, metal, industrial, and indie rock have all become recognized and respected, and all fall in some way beneath the "rock" umbrella. What these disparate "genres" share is a tendency toward guitar-based music and liberated emotional expression. That's about as far as we're willing (or able) to go in defining and describing rock. Now the question is: what are you doing sitting here reading this when you could be indulging yourself in the ecstasy of rock and roll?