Webster's 1828 Dictionary
ORILLON
n.In fortification, a rounding of earth, faced with a wall, raised on the shoulder of those bastions that have casemates, to cover the cannon in the retired flank, and prevent their being dismounted.
Webster's 1913 Dictionary
ORILLON
O *ril "lon, n. Etym: [F., lit. , a little ear, from oreille an ear, fr. L. oricula, auricula, dim. of auris an ear. See Ear. ] (Fort. )
Defn: A semicircular projection made at the shoulder of a bastion for the purpose of covering the retired flank, -- found in old fortresses.
The Wordsmith Dictionary