1. 请愿者
A petitioner is a person who presents or signs a petition.

2. 诉愿人；上诉人
A petitioner is a person who brings a legal case to a court of law.

3. 上诉请求离婚者
A petitioner is someone who goes to a court of law to ask for a divorce.

1. one praying humbly for something

e.g. a suppliant for her favors

Synonym: suppliantsupplicantrequester

2. someone who petitions a court for redress of a grievance or recovery of a right

Synonym: suer