Noun
akathist (plural akathists)
(Christianity) A hymn dedicated to a saint, holy event, or person of the Holy Trinity, in Eastern Christian traditions. [1853]
Saturday of the Fifth Week is dedicated to the Theotokos (Mother of God), and is known as the "Saturday of the Akathist" because the Akathist to the Theotokos is chanted during Matins on that day (again, usually anticipated on Friday evening). Source: Internet