IPA: /ˈhɛəˌsprɪŋ/
KK: /ˈhɛrˌsprɪŋ/
A thin, coiled spring used in watches and clocks to control the movement of the balance wheel.
The watchmaker carefully adjusted the hairspring to ensure the timepiece kept accurate time.
Hairspring → The word is formed from "hair" (from Old English *haer*, meaning the fine strands growing from the skin) and "spring" (from Old English *springan*, meaning to leap or jump). A hairspring is a fine spring used in watches that helps regulate time, akin to the delicate nature of hair.
Think of fine 'strands' ('hair') that 'leap' or 'move' ('spring') to help keep time in a watch.