Definitions
1.nounA back gate, back door, side entrance, or other gateway distinct from the main entrance.
2.nounBy extension, a separate or hidden way in or out of a place, situation etc.
3.nounA subterranean passage communicating between the parade and the main ditch, or between the ditches and the interior of the outworks.
4.adjectiveSituated at the rear; posterior.