From BiblePortal Wikipedia

Webster's Dictionary [1]

(1): ( n.) The Book of Psalms; - often applied to a book containing the Psalms separately printed.

(2): ( n.) A rosary, consisting of a hundred and fifty beads, corresponding to the number of the psalms.

(3): ( n.) Specifically, the Book of Psalms as printed in the Book of Common Prayer; among the Roman Catholics, the part of the Breviary which contains the Psalms arranged for each day of the week.

Holman Bible Dictionary [2]

 Psalm 2:1

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [3]

This word is often used by ancient writers for the book of Psalms, considered as a separate book of Holy Scripture. It obtained among later Church writers a more technical meaning as the book in which the Psalms are arranged for the service of the Church. The Roman Catholic Psalter, for instance, does not follow the Scriptural order of the Psalms, but arranges them for the various services in a different manner. In the English Psalter, as it exists in the Book of Common Praver, the Psalms are arranged in such a way as to give a reading for every day in the month, and there are also special selections to be used in the discretion of the ininister. The translation is not that of the King James Version (i.e. our common Biblle), but the earlier version of Cranmer's Bible, which accounts for the difference between the Psalms of the Prayer-book and those of the ordinary version of the Bible. The use of the Psalter as a system of psalmody seems to have been borrowed from the synagogue. The Psalter was always a favorite book, and one which obtained a most extensive use both in private and public. It was regarded as an epitome of the Bible, and as especially adapted to the use of youth and the people at large. The clergy were required to commit this book to memory. In later times, when the Bible as a whole was denied to the people, the Latin Psalter was left in their hands; and at the time of the Reformation the penitential psalms were in the hands and mouths of the people.

Sometimes the book, for the sake of convenience, was dividedl into five portions, to correspond with the Pentateuch; and again the Psalms were arranged in different classes according to their character, as hallelujah, baptismal, penitential. burial psalms, etc. In the time of St. Augustine and St. Chrysostom the burial psalms were 23, 42, 43, 59, 101; in the Roman Church they are 23, 25, 27 and the seven penitentials; in the English Church, 33, 90; in the Greek Church, 91, 119; and for clerks, 24, 84. Beleth mentions Psalms 114 and Confitemini; he says charcoal was placed in the grave to show that the ground could never again be occupied. Psalms Gradual, Pilgrims' Songs, or Psalms of Degrees, were Psalms 120-134, which were sung in ascending the fifteen steps of Solomon's Temple. Hallelujah Psalms were 146 to 150, each beginning with the words "Praise ye the Iord." Psalms Lucernal were those suing in the primitive Church at the lighting of the lamps the first hour of the night. The Clementine Constitutions, Cassian, and St. Chrysostom mention the office said at this time under the same appellation. Psalms of Praise (Hallel) were Psalms 113-118, the hymn slung by Christ before his agony. Psalms Penitential were seven: St. Augustine, when dying and lying speechless on his bed, had the seven psalms painted on the walls of his chamber, that, looking towards them, he might resist any temptations of the devil (Psalm 6, 32, 38. 51 [Miserere], 102, 130 [De Profundis], 143). Psalms Prostrate were those during the saying of which seniors knelt in their stalls and the junior monks lay prostrate on the floor or forms. These were said after vespers and in Lent, before the Collects of the Hours and Verba mea auribus percipe. Twelve psalms, called the Dicta, were sulng, (with three lections anil responsories and six anthems) on the nocturnus of ordinuary days, one for each hour of the night. Six, says Beleth, are sung at matins, lauds, and other hours, in memory of the six works of mercy; five at vespers, one for each of the senses; and four at compline, the number of perfection.