• Webster's Revised Unabridged Dictionary
    • n Labarum The standard adopted by the Emperor Constantine after his conversion to Christianity. It is described as a pike bearing a silk banner hanging from a crosspiece, and surmounted by a golden crown. It bore a monogram of the first two letters (ΧΡ) (which appear like the English letters X and P), of the name of Christ in its Greek form. Later, the name was given to various modifications of this standard.
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Century Dictionary and Cyclopedia
    • n labarum A Roman military standard adopted by the later emperors as the imperial standard. It consisted of a staff or lance carrying a purple banner on a cross-bar. This banner usually bore the effigy of the general or emperor; but Constantine the Great, after his conversion, placed upon it, woven in gold, the cross and the monogram (chrisma) or emblem of Christ, or , consisting of the Greek letters XP (Chr), standing for Christ. In later times the name was given to the monogram itself, or to the cross in the monogram.
    • n labarum A standard or banner of similar form, borne in ecclesiastical processions of the Roman Catholic Church.
    • n labarum Figuratively, a moral standard, guide, or device.
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Chambers's Twentieth Century Dictionary
    • n Labarum lab′a-rum a Roman military standard adopted as the imperial standard after Constantine's conversion. It bore the Greek letters XP (Chr), joined in a monogram, to signify the name of Christ: a similar ecclesiastical banner borne in processions: any moral standard or guide.
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Webster's Revised Unabridged Dictionary
Chambers's Twentieth Century Dictionary
Late Gr. labaron, origin unknown. Some make bold to derive from Basque labaria, a standard.


In literature:

Under Jovian, Christianity was established as the state religion, and the Labarum of Constantine again became the standard of the army.
"Encyclopaedia Britannica, 11th Edition, Volume 15, Slice 5" by Various