a cat whose job it is to CATch rats.
often used when mousetraps would be inconvenient because you could step on then or if somebody lieks cats as a pet.
'Hey Jake, so why are we here on this sunny day at such an indoor pet shop?'
'Well Joseph, I'm here to get me a ratcat.'
'Ratcat? Sorry Jake, i'm unfamiliar with the phrase.'
'Then go look it up on urbandictionary, i don't have time to explain for I'm busy buying a ratcat.'