Wiktionary
intervenor
alt. one who intervenes, especially relating to law. n. one who intervenes, especially relating to law.
WordNet
intervenor
n. (law) a party who interposes in a pending proceeding
Usage examples of "intervenor".
The Brendan Tuoheys of the world had bagmen and intervenors and a thousand layers of protection.
Fortune and chance, twin powers of atevi belief, intervenors in the rigid tyranny of numbers.