a wheel which imparts regularity to the movements of any engine or machine; a fly wheel.
2. balance wheel ·- 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.
3. balance wheel ·- a ratchet-shaped scape wheel, which in some watches is acted upon by the axis of the balance wheel proper (in those watches called a balance).