caveator
/kæˈveɪtər/Definitions
1. noun
A person who starts a lawsuit, especially one who sues on behalf of a municipality or other public entity.
“The city’s attorney served as the caveator in the case against the environmental polluter.”
2. noun
A person who opposes or contests something, especially a will or a document.
“The caveator questioned the legitimacy of the deceased’s will in court.”