zip fastener UK /ˈzɪp ˌfɑːs(ə)nə/US /ˈzɪp ˌfæs(ə)nɚ/ noun2 •A fastener used in clothing, bags, etc, comprised of two rows of teeth that are made to fit into each other by moving a slider along their length and opened again by moving the slider in the other direction. •A pressure-sensitive plastic closure. formszip fasteners