noun
: a center pinion gear of a watch that unscrews when the mainspring breaks and relieves the pressure on the delicate train wheel teeth and arbor pivots
noun
: a center pinion gear of a watch that unscrews when the mainspring breaks and relieves the pressure on the delicate train wheel teeth and arbor pivots
Webster's New International English Dictionary. Новый международный словарь английского языка Webster. 2012