Dictionary.net

a wheel that regulates the rate of movement in a machine; especially a wheel oscillating against the hairspring of a timepiece to regulate its beat

A wheel which regulates the beats or pulses of a watch or chronometer, answering to the pendulum of a clock; - often called simply a balance.

A wheel which regulates the beats or pulses of a watch or chronometer, answering to the pendulum of a clock; - often called simply a balance.