a person who is being extremely annoying. It is a combination of the words rat and asshole. It can be used in anger or towards a friend in a joking matter.
Wow omg I cant believe you stole my cookie, you’re such a rat hole.
A person or friend, outside an entity to secretly move money or launder money making it appear to have earned money legally.
He persuaded friends outside the company to act as “rat holes”, handing them stakes in each new issue, which would belong to that person on paper, but which, in fact, would be originator's money and originator’s stake.
Madefamous by the TWIT podcast Macbreak Weekly, a rat hole is when a discussion follows a constant tangent and ends up with a topic that has nothing to do with the original discussion.
To digress in an extensive way. To divert the conversation to a topic that is not only unrelated to the topic at hand, but a topic that will likely have no immediate resolution either.
That's an interesting discussion, but let's stay on track and not go down a rat-hole.