Emily Dickinson Lexicon

PORT-CUL'LIS, n. [coulisse, in French, is from couler, to flow or slip down. It signifies a groove or gutter. I think it can not be from L. clausus.]

In fortification, an assemblage of timbers joined across one another, like those of a harrow, and each pointed with iron; hung over the gateway of a fortified town, to be let down in case of surprise, to prevent the entrance of an enemy. – Encyc.