Proprio motu is a Latin term that means 'on one's own initiative'. There are many synonyms for this term that can be used in different contexts. Some of the most common synonyms include self-initiated, spontaneous, voluntary, independent, autonomous, and under one's own steam. Each of these terms emphasizes the idea of taking action or making a decision without being prompted or instructed by someone else. For instance, someone may take a course of action proprio motu, without being told what to do by anyone. These synonyms can be used interchangeably to convey the same idea.