Emily Dickinson Lexicon

RAV'EL-IN, n. [Fr. id.; Sp. rebellin; Port. rebelim; It. ravellino.]

In fortification, a detached work with two faces which make a salient angle, without any flanks, and raised before the counterscarp of the place. In this it differs from a half moon, which is placed before an angle. – Encyc. Dict.