Sideboob -- that's like so five minutes ago! It's sidebum that's become one of the biggest trends in fashion. The style, which shows just a flash of skin or of the butt cheek, has been on the rise for over a year now.

While it might seem as though sideboob is super scandalous, since it shows off a little too much and can lead to a nip slip, sidebum is even more terrifying, since it pretty much requires the wearer to go commando aka sans undies, since you can't really have pantylines with sidebum. And we all know what happens when said starlet gets out of a car!

Still, it remains a dangerous fashion "do."

Also, sidebum comes in all shapes, sizes and lengths. It can be just a hint, a slit, or a sexy flash of skin, covered by fabric. Or it can be a full on butt-baring look, where the air hits the flesh. The sidebum look often incorporates the thigh and the length of the leg, too.

There are so many varieties of sidebum! We've seen 'em all! The one constant is that sidebum shows off the shapely, round and curvaceous derriere in several sexified ways.

Repeat sidebum offender Gwyneth Paltrow in Pucci.

Frazer Harrison, Getty Images

And in Antonio Berardi, which is much racier. What shapely stems (and bootay) you have, Gwynnie!

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Whoa! 'Thor' actress Jaimie Alexander isn't sidebumming it. She's onecheeking it.

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Miley Cyrus shows off a hint of sidebum in this slinky LBD with cutouts.

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See Zoe Saldana's perfect curve.

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Taylor Swift doesn't always show skin, but this is subtle sidebum.

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Upon closer inspection...it's more like an optical illusion created by two-toned fabric. It still counts.

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Kate Winslet's Stella McCartney frock is classic in its sidebum flash.

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Ashley Tisdale sparkles while she sidebums it!

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Kelly Rowland dares to sidebum in Georges Chakra.

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Selena Gomez's sidebum is red hot Reem Acra.

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Julianne Hough stood out and not because her dress was neon in hue.

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With a bootay as famous as hers, J. Lo has to show sidebummage in Kaufman Franco.

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That's Heidi Klum's back sidebum.

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Here's the front view. Sideboob, too.

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Kesha's Givenchy LBD is really a LSBD aka little sidebum black dress.

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Rihanna's sidebum was encased in a spiral-shaped Jean Paul Gaultier dress.

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A crimson concoction where the British singer Jessie J shows sidebum! Weeee!

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Actress Jena Malone couldn't let this trend pass her by, thanks to her Nicholas Oakwell dress.

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Bella got back! Kristen Stewart and her round rump...whoa!

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Kristyn Ritter rocked fishnet, but it was more like sidethigh.

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