Pronunciation: (är'sis),[key] —n., —pl.-sesPronunciation: (-sēz).[key] 1. Music.the upward stroke in conducting; upbeat. Cf. thesis (def. 4).
2. Pros. a. the part of a metrical foot that bears the ictus or stress.
b. (less commonly) a part of a metrical foot that does not bear the ictus. Cf. thesis (def. 5).