T'Gha maneuver
The T'Gha maneuver was an illegal move in bat'leth competitions. 

In an alternate reality experienced by Worf in 2370, he lost a bat'leth tournament because his opponent used the T'Gha maneuver against him, which the judges chose to ignore. He suffered a blow to the head as a result of the maneuver, which left him with a concussion. Worf detailed his 9th place finish in his personal log. ()
Maneuvers
Sports rules and regulations