[ar.sis] n, pl ar.ses [LL & Gk; LL, raising of the voice, accented part of foot, fr. Gk, upbeat, less important part of foot, lit., act of lifting, fr. aeirein, airein to lift] (14c) 1 a: the lighter or shorter part of a poetic foot esp. in quantitative verse b: the accented or longer part of a poetic foot esp. in accentual verse
2: the unaccented part of a musical measure--compare thesis