Wiktionary
n. A percussion instrument used chiefly in Eastern Orthodox monasteries to summon the brethren to prayer or to lead processions.
Wikipedia
The semantron or semandron , or semanterion , also called a xylon (; Russian: било, bilo; Bulgarian, Macedonian and Serbian: клепало, klepalo) is a percussion instrument used in monasteries to summon the monastics to prayer or at the start of a procession.
Usage examples of "semantron".
From the weathered, low building came the clamor of a wooden semantron and bells, summoning the pious to worship.
The hollow notes of the wooden semantrons and monks chanting echoed out over the water.
Byzantine convents: the massed voices, and the semitones, the striking of wood semantrons, and the incense, floating below the long, melancholy features of the Figures in Majesty, glittering in mosaic.