The Collaborative International Dictionary
Holiness \Ho"li*ness\, n. [AS. h[=a]lignes.]
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The state or quality of being holy; perfect moral integrity or purity; freedom from sin; sanctity; innocence.
Who is like thee, glorious in holiness!
--Ex. xv. 11. -
The state of being hallowed, or consecrated to God or to his worship; sacredness.
Israel was holiness unto the Lord.
--Jer.ii. -
His holiness, a title of the pope; -- formerly given also to Greek bishops and Greek emperors.
Syn: Piety; devotion; godliness; sanctity; sacredness; righteousness.
Wikipedia
His Holiness is a style and form of address (in the variant form Your Holiness) for supreme religious leaders, originally and most notably the Pope.
Usage examples of "his holiness".
Whatever else was true about the tales of the rogue ship Raphael, it was uncontestable that His Holiness's Crusade against the Ousters had been set back years by the hit-and-run attacks.
It is also true that His Holiness introduced an interesting paradox.