"backstairs" in the noun sense
1. backstairs
a second staircase at the rear of a building
"backstairs" in the adjective sense
1. backstair, backstairs, furtive
secret and sly or sordid
"backstairs gossip"
"his low backstairs cunning"- A.L.Guerard
"backstairs intimacies"
"furtive behavior"
Source: WordNet® (An amazing lexical database of English)
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