Verb
rat on (third-person singular simple present rats on, present participle ratting on, simple past and past participle ratted on)
(transitive) To tattle, squeal about (someone)
You learned the two greatest thing in life, never rat on your friends, and always keep your mouth shut. Robert De Niro
I play a lot of games on my iPhone. There is a game called Rat on a Scooter that I will promote as much as possible because it has brought me so much joy. Jonah Hill