Entry 1 sense Webster, 1913 Hairpin /(-pĭn`)/ · Hair·pin · IPA /ˈhɛɚ.pɪn/ 01 n. A pin, usually forked, or of bent wire, for fastening the hair in place, -- used by women. 1. A pin, usually forked, or of bent wire, for fastening the hair in place, -- used by women.