Pronunciation : XP. [Belongs here in appearance only.]
Definition : Defn: The first two letters of the Greek word XRISTOS, Christ; -- an abbreviation used with the letters separate or, oftener, in a monogram, often inclosed in a circle, as a symbol or emblem of Christ. It use as an emblem was introduced by Constantine the Great, whence it is known as the Constantinian symbol, or monogram. See Labarum.
Source : Webster's Unabridged Dictionary, 1913