noun Horology.

a fixed end of a spiral hairspring, consisting of an upwardly and inwardly bent continuation of the outermost coil of the spring: used to offset the asymmetry of the common spiral spring when tight, which impairs isochronism.
a hairspring having such a fixed end.

Origin of overcoil

First recorded in 1880–85; over- + coil1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for overcoil

Historical Examples of overcoil