Толковый словарь английского языка - arsis

noun (plural arses) Etymology: Late Latin & Greek; Late Latin, raising of the voice, accented part of foot, from Greek, upbeat, less important part of foot, literally, act of lifting, from aeirein, airein to lift Date: 14th century 1. the lighter or shorter part of a poetic foot especially in quantitative verse, the accented or longer part of a poetic foot especially in accentual verse, the unaccented part of a musical measure