U.S. gymnast Simone Biles said she got the ‘twisties.’ Here is what that means.

Star gymnast Simone Biles withdrew from Thursday’s all-around competition at the Tokyo Olympics “to focus on her mental health,” USA Gymnastics said Wednesday.

“Simone will continue to be evaluated daily to determine whether or not to participate in next week’s individual event finals,” the organization said in a statement.

“We wholeheartedly support Simone’s decision and applaud her bravery in prioritizing her well-being. Her courage shows, yet again, why she is a role model for so many.”

Biles, the four-time gold medalist, flew off the mat during a floor exercise on Sunday and then stumbled on the vault.

The Washington Post noted Biles planned to perform a 2 1/2 twisting vault “but her mind chose to stall after just 1 1/2 twists instead.”

“They saw it a little bit in practice.. having a little bit of the ‘twisties’,” Biles told reporters.

What ‘twisties’ are

It’s not that different from an athlete having the “yips.” But unlike former MLB player Chuck Knoblauch having trouble throwing to second base, a gymnast with the “twisties” can lose his or her bearings while in the air. That can be a dangerous situation.

Gymnasts frequently flip and twist at the same time and the mind knows how and where the body is moving. CNN called it “proprioception, a sense of where your body is in space and what it’s doing.”

Usually, a gymnast’s mind can process those two requests. But when it doesn’t, the “twisties” can occur.

Gymnast Giulia Steingruber said in the documentary “The Hard Way To Success” that she got the “twisties” in the summer of 2014.

“When I wanted to twist, especially on vault, I had no feeling where I am. I was really scared and I was afraid to do it,” Steingruber said. “It was quite tough for me, because I didn’t understand why it came, and I couldn’t stop it. So it was just strange for me and it was horrible.”

Sean Melton, a former gymnast, told the Washington Post why it can be unsafe to continue while having the “twisties.”

“Simply, your life is in danger when you’re doing gymnastics,” Melton said. “And then, when you add this unknown of not being able to control your body while doing these extremely dangerous skills, it adds an extreme level of stress. And it’s terrifying, honestly, because you have no idea what is going to happen.”

Former gymnast Jacoby Miles said her neck was broken after a case of the “twisties” and applauded Biles’ decision to sit out.