A man engaging in vigorous sexual congress with a woman who posesses a unkempt bush can be said to be 'feeding the rat'
A man joins assorted friends for breakfast following a heavy night out:
Man: "Goodness, you should have seen the size of the badger on the bird i pulled last night, I almost lost my kebab"
Mate #1: "Did you feed the rat?"
Man: "Yeah, I managed to throw a flacid semi up her"