noun
: a timepiece balance wheel so constructed (as of two metals of different expansivities) that variations of temperature produce such changes in its mean rim diameter as offset the changes produced in the hairspring
noun
: a timepiece balance wheel so constructed (as of two metals of different expansivities) that variations of temperature produce such changes in its mean rim diameter as offset the changes produced in the hairspring
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012