1.Small rodent with long tail. Lives in sewers. Smells like shit.
2. A person you generally do not want to be around.
3. Piece of shit
"Man that guy is such a rat"
"That rat smells like shit!"
"I saw this guy, Chris, at the party last night. Not only did he smell like shit, but he was such a rat!"
Mate look at at that lovely bit of rat over there. Or more simply the word rat can be called from any male member of the group who believes he has spotted a rather sexy chick. Upon which the other males will soon scan the area for the potential rat and either give their approval or disgust. False calling of this word is highly frowned upon.
A really ugly, or fat or sluttygirl or a combination of all. She looks dirty, hangs around dirty bogan places and has fucked many times with ugly dirty guys
"OMFG, Taney'ls such a filthy rat"
"I know. And she fucked Martin 13 times!"