1. The leader of a circle of dancers; hence, the leader of a number of persons acting together; the leader of a herd of animals.
A primacy of order, such an one as the ringleader hath in a dance. --Barrow.
2. Opprobriously, a leader of a body of men engaged in the violation of law or in an illegal enterprise, as rioters, mutineers, or the like.
The ringleaders were apprehended, tried, fined, and imprisoned. --Macaulay.
n : a person who leads (especially in illicit activities)