passion pit

noun2

1. •
   (slang) A drive-in theatre or other unlit or dimly-lit secluded public or private location, with particular reference to it as a place of intimacy.

   • The men who worked in it called it the Passion Pit in wry remembrance of other dark rooms they had known and used for more intimate and more enjoyable purposes... — 1952
2. •
   (slang) Any place where sexual activity commonly occurs.

   • As relationships mature, the bedroom gets de-coupled from its former role as a passion pit and instead becomes a place to zonk out, watch TV or work. — 1996