processional

Of, pertaining to, or used during a procession, particularly at the start of a religious ceremony or wedding.

The publick Processional-way to the Chapter-house at Windesor, used time out of mind, led from the Presence-Chamber, down through the Cloister, and the great Gate of the Kings Lodging, into the upper Ward of the Castle, thence through the middle Ward, and part of the lower, to and through the passage, between the East-end of the Chappel, and Tomb-house, and thence into the Chapter-house, situate at the North-East Corner of St. George’s Chappel.

1799, Isaac D’Israeli, Mejnoun and Leila, the Arabian Petrarch and Laura, Book 4, in Romances, London: Cadell and Davies et al., pp. 170-171, The nuptial day arrives. The virgin, preceded by a splendid retinue, and followed by her mother, her female relatives, and the damsels of her tribe, issues from the tent of her father. […] The women then followed with solemn and processional steps.

A hymn or other music used during a procession; prosodion.

A perfectly drilled wedding procession, like a military one, should move forward in perfect step, rising and falling in a block or unit. To secure perfection of detail, the bars of the processional may be counted so that the music comes to an end at precisely the moment the bride and groom stand side by side at the chancel steps.

[…] a rainy Palm Sunday. […] At Grace Church on-the-Hill, the children and the acolytes stood huddled in the narthex; holding their palm fronds, they resembled tourists who’d landed in the tropics on an unseasonably cold day. The organist chose Brahms for the processional—“O Welt ich muss dich lassen”; “O world I must leave you.”

A group of people or things moving along in an orderly, stately, or solemn manner.

He saw the processional of world brotherhood tramp steadily through the paling sunset; saffron-vestured Mandarin marching by flax-faced Norseman and languid South Sea Islander—the diverse peoples toward whom he had always yearned.

And Eugene watched the slow fusion of the seasons; he saw the royal processional of the months; he saw the summer light eat like a river into dark; he saw dark triumph once again; and he saw the minute-winning days, like flies, buzz home to death.

A service book relating to ecclesiastical processions.

[47] Item that the Churchwardens of euery paryshe shall delyuer vnto our visitours the inuentories of vestmentes, copes, and other ornamentes, plate, bookes, and specyallye of Grayles, Couchers, Legendes, Processionalles, Hymnalles, Manuelles, Portuesses, and suche lyke apperteynyng to theyr Church.

c. 1640s, John Gregory, “Episcopus Puerorum In Die Innocentium: Or, A Discovery of an Ancient Custom in the Church of Sarum, making an Anniversary Bishop among the Choristers” in The Works of the Reverend and Learned Mr. John Gregory, London: R. Royston and T. Williams, 1671, p. 114, By the Use of Sarum (for ’tis almost the only place where I can hear any thing of this; that of York in their Processional seems to take no notice of it) upon the Eve to Innocents Day the Chorister-Bishop was to go in solemn Procession with his fellows […]