Bizarre optical illusion has people either seeing a car door or the beach.

If you spend much time reading about music on the Internet, there’s a good chance you’ve learned about a supposed revival of the "butt rock" genre. It’s a slippery and loosely defined term—one thrown around in both derogatory and affectionate ways, depending on the source. But these days, it’s widely used to describe the crop of guitar-heavy bands, including Creed and Nickelback, that emerged during the post-grunge bloom of the late '90s and early 2000s. Now that this millennial-friendly music has reached a certain vintage, it’s officially entering "classic rock" territory—a depressing reminder of mortality for anyone who may have owned a pair of JNCO jeans or browsed the CD-singles section at FYE.

But let’s back up for a second. Where did this whole label even come from? One widely circulated theory claims that it originated as a spin on the tag lines of certain alternative radio stations from this era—the ones that specialized in "nothing but rock." Others say the phrase dates back further: Stephen Kallao, a contributing host of World Cafe, the syndicated radio show from Philadelphia station WXPN, says "butt rock" refers to the "very machismo, hyper-sexualized cousin of glam rock" that emerged in the late '70s and early '80s. No one has concrete answers, but there does seem to be a clear consensus, at least by 2025 standards, on the definitive bands.