Emily Dickinson Lexicon

SAL'LY-PORT, n.

1. In fortification, a postern gate, or a passage under ground from the inner to the outer works, such as from the higher flank to the lower, or to the tenailles, or to the communication from the middle of the curtain to the ravelin. – Encyc.
2. A large port on each quarter of a gireship, for the escape of the men into boats when the train is fired. – Mar. Dict.