You've heard the term: "Butt rock." But what exactly is butt rock — and why is it called that? Have you ever come to the defense of one of your favorite bands after they were called butt rock?

Because the expression is used to disparage some hugely popular artists. But who were the first rockers to earn the dubious distinction, and how did they come to embody what became known as butt rock? These days, the catch-all encompasses at least two different eras of rock, depending on who you ask.

What bands come to mind when you hear the term? An overview on the website Overthinking It mentions Motley Crue, Creed and Puddle of Mudd as examples of groups one might call butt rock. The top definition at Urban Dictionary cites Five Finger Death Punch, Nickelback and Buckcherry. But how much does that track with listeners on a broad scale?

What drives one to label groups butt rock in the first place? Does it come down to the music, the look, the attitude? Is there some innate quality that lands a band with the infamous tag?

It's no laughing matter. Or maybe it is. Look through the gallery below to consider butt rock's past, present and future. Because, who knows, maybe some of your favorite music will be included in the annals of butt rock history.

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