Wiktionary
detangler
n. A product for removing tangles from hair.
Wikipedia
Detangler
The detangler or rotor is an invention for the freestyle BMX bicycle, allowing the handlebars to turn a complete 360° rotation without the brake cables getting tangled up. It is commonly called the Gyro. The trademark for the term Gyro is owned by Odyssey BMX, of Cerritos, California. SST oryg is another common manufacturer of detangler systems.
A detangler is usually only used for the rear brake. The front brake cable can be routed through the stem, via a hollow stem bolt known as a Pott's mod bolt, and fork steer tube to avoid the tangling problem.