Other forms: mutinied; mutinies; mutinying
A mutiny is a rebellion against authority, like when sailors overthrow the captain of a ship or when a class of 8th graders refuses to dissect a frog in biology class.
Mutiny comes from an old verb, mutine, which means "revolt," and a mutiny is still like a revolt. It can be a group of people, like in the famous Mutiny on the Bounty in 1789 when the crew of a British Royal Navy ship kicked the captain out so they could stay in Tahiti. (Totally worth it.) Mutiny also means "to refuse the order of the person in authority," so it doesn't always take place at sea or in the military, it can happen in a classroom and be every teacher's nightmare!