Word Study
back door
CIDE DICTIONARY
back door,
A door in the back part of a building; hence, an indirect way. Atterbury. [1913 Webster]
THESAURUS
back door
French door, afterpart, afterpiece, archway, back, back road, back seat, back side, back stairs, back street, back way, backstairs, barway, behind, bolt-hole, breech, bulkhead, by-lane, bypass, bypath, byroad, bystreet, byway, carriage entrance, cellar door, cellarway, clandestine, covert, covert way, detour, door, doorjamb, doorpost, doorway, escalier derobe, escape hatch, escape route, feline, front door, furtive, gate, gatepost, gateway, hatch, hatchway, heel, hidlings, hind end, hind part, hindhead, hole-and-corner, hugger-mugger, lintel, occiput, porch, portal, porte cochere, posterior, postern, privy, propylaeum, pylon, quiet, rear, rear end, rearward, reverse, roundabout way, scuttle, secret exit, secret passage, secret staircase, shifty, side door, side road, side street, skulking, slinking, slinky, sly, sneaking, sneaky, stealthy, stern, stile, storm door, surreptitious, tail, tail end, tailpiece, threshold, tollgate, trap, trap door, turnpike, turnstile, under-the-counter, under-the-table, undercover, underground, underground railroad, underground route, underhand, underhanded, unobtrusiveFor further exploring for "back door" in Webster Dictionary Online