lab·a·rum 
(lăbər-əm)
(lăbər-əm)n. pl. lab·a·ra (-ər-ə)
1. An ecclesiastical banner, especially one carried in processions.
2. The banner adopted by Constantine I after his conversion to Christianity.
[Late Latin, probably from alteration of Greek labrāton, laurel-leaf standard, from Latin laureātum, neuter of laureātus, adorned with laurel; see LAUREATE.]