1) Christian symbol 
moral standard; ecclesiastical banner bearing Christ's monogram
• (n.) 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 (CHR) of the name of Christ in its Greek form. Later, the name was given to various modifications o...
sacred military standard of the Christian Roman emperors, first used by Constantine I in the early part of the 4th century . The labarum—a Christian ...
Military standard of the Christian Roman emperors, an adaptation of the older cavalry standard. It was first used in 312 by Constantine the Great. ...
The Byzantine military standard of Constantine the Great, which included the chi-rho sign. 
Lab'a·rum noun ; plural Labara . [ Latin ] 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 (
A labarum is a standard or banner carried in Christian religious processions.