Noun
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 of this standard.
Source: Webster's dictionaryA Companion to Roman Religion edited by Jörg Rüpke 2011 ISBN 1-4443-3924-9 page 159 Eusebius stated that in addition to the singular labarum of Constantine, other similar standards (labara) were issued to the Roman army. Source: Internet
AD 337) showing a depiction of his labarum spearing a serpent. Source: Internet
Ancient sources draw an unambiguous distinction between the two terms "labarum" and "Chi-Rho", even though later usage sometimes regards the two as synonyms. Source: Internet
At the focal point of the basilica, a stone statue of Constantine holding the Christian labarum in its hand was erected. Source: Internet
He made extensive use of the Chi-Rho and the labarum only later in the conflict with Licinius. Source: Internet
Smith, 104: "What little evidence exists suggests that in fact the labarum bearing the chi-rho symbol was not used before 317, when Crispus became Caesar.. Source: Internet