Lewis & Short

lăbărum, i, n., = λαβαρόν, the labarum, a Roman military standard of the later times, richly ornamented with gold and precious stones, and bearing the effigy of the general. Constantine the Great placed upon it a crown, a cross, and the initial letters of the name Jesus Christus, and made it the imperial standard, Prud. ap. Symm. 1, 487; Tert. Apol. 16.