Noun

1. a leader of a group of people, especially an unofficial group
2. a person who starts and leads a disturbance (such as a riot), a conspiracy, or a criminal gang
   • The police arrested the ringleaders of the smuggling operation.
   • (1590): William Shakespeare, King Henry VI, Part 2: A sort of naughty persons, lewdly bent, / Under the countenance and confederacy / Of Lady Eleanor, the protector's wife, / The ringleader and head of all this rout, / Have practis'd dangerously against your state...