Entry 2 senses · 2 variants Webster, 1913 Caplin /kăp'-lĭn/ · Cap·lin · IPA /kˈæplɪn/ n. n. 01 n. See Capelin. 1. See Capelin. See: Capelin 02 n. The cap or coupling of a flail, through which the thongs pass which connect the handle and swingel. 1. The cap or coupling of a flail, through which the thongs pass which connect the handle and swingel.