tripleback
/ˈtrɪbəlbæk/Definitions
1. noun
A person who has backed out or reneged on an agreement.
“The company felt betrayed by their former business partner, who turned out to be a tripleback.”
2. noun
A person who gives false testimony or support, often in exchange for personal gain.
“The witness was revealed to be a tripleback, deliberately misleading the court to cover their own tracks.”