Entry 2 senses · 2 variants Webster, 1913 Yin /yĭn/ · IPA /jɪn/ n. n. 01 n. A Chinese weight of 2<frac:2_3/ pounds. 1. A Chinese weight of 2<frac:2_3/ pounds. 02 n. one of the two fundamental principles. See yin and yang. 1. one of the two fundamental principles. See yin and yang.(Chinese philosophy) See: yin and yang