ˈpe.trənəl noun
( -s )
Etymology: perhaps modification of Middle French petrinal, alteration of poitrinal, from poitrinal, adjective, of the chest, from poitrine chest, breast (from assumed Vulgar Latin pectorina, from feminine of assumed Vulgar Latin pectorinus, adjective, of the breast, from Latin pector-, pectus breast + -inus -ine) + -al — more at pectoral
: a portable firearm resembling a carbine of large caliber and fired with the butt resting against the chest