An ugly rodent with oversized front teeth used to gnaw through just about anything.
Origins: Derives from the verb: 'To Rat/To Rat on' - To seriously go after a female with the purpose of pulling them.
Dave: He's been with that bird all night, apparently he's been texting her all week. Think she's going back to his house.
Dan: He kept that quiet! He's such a sewer rat!