Cathisma is a section of the psalter.
(1) The psalter in the Greek office is divided into twenty sections, called cathismata. Each cathisma is subdivided into three stases, and "Gloria" is said at the end of each stasis only. The reason for the name assigned is that, while the choir stand two and two by turns to recite the psalms, the rest sit down.
(2) A short hymn which occurs at intervals in the offices of the Greek Church. It consists of one stanza or troparion (posrapowi), and is followed by "Gloria." The name is said to indicate that while it is sung the choir sit down' for rest.