Entry 2 senses · 2 variants Webster, 1913 Sis /sĭs/ · IPA /sɪs/ n. n. 01 n. A colloquial abbreviation of Sister. 1. A colloquial abbreviation of Sister. See: Sister 02 n. Six. See Sise. 1. Six. See Sise.[Obs.] See: Sise