petitioner

noun

Etymology: From petition + -er. Doublet of petitionary.

1. Someone who presents a petition to a court.

   “The Supreme Court said Monday that unanimous jury verdicts are required in state criminal trials for serious offenses, handing a victory to criminal defendants including petitioner Evangelisto Ramos, who was convicted of murder in Louisiana on a 10-2 vote. […] In court, a lawyer for Louisiana argued that if the Supreme Court were to rule in favor of Ramos the ruling could apply to some 32,000 people that are currently serving time for serious crimes because thousands of petitioners would come to the court demanding relief.”

2. Someone who presents a petition to some person in authority.

   “Ethel was in mourning: they had judged it the most fitting habit for a petitioner; it was certainly one most becoming to the wearer.”