A dude competing for a chick's affections who brings legal action against her for some ruined-romance-related matter, such as her not "being loyal" to or spending a promised amount of time with him, failing to return money dat he'd loaned her and she'd promised to pay back if she started dating someone else, etc.
A lady should be very careful how she treats the special men in her life --- a rival SUITOR can quickly become a rival SUEDHER; this term can also sometimes even mean one of two or more "old flame" plaintiffs who ALL feel dat she has wronged them in some way.