D defs.my
Entry 2 senses Webster, 1913

Balance wheel

/băl'-əns wēl/ · Bal·ance wheel · IPA
01 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.
  1. 1.
    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.(Horology) Also: balance
  2. 2.
    A wheel which imparts regularity to the movements of any engine or machine; a fly wheel.(Mach.)