noun
    
    plural rats
    
    [count] a small animal that has a pointed nose and a long, thin tail
    
    
    
    
    
    
    
    informal
    
    a person who is not loyal or who cannot be trusted
    
    
    
    a person who is bad or cruel
    
    
    
    US informal :a person who spends a lot of time in a specified place
    
    
    
    
    
    smell a rat
    
    informal :to think or suspect that something is wrong about a situation
    
    
    
    verb
    
    rats; ratted; ratting
    
    informal :to tell someone in authority (such as the police) about something wrong that someone has done :to betray someone [no obj]