Hop Joint Meaning

(idiomatic) Place where opium is smoked.

Example: 1915, George Bronson-Howard, God's Man, page 39:
  There's quite a trade in laudanum since the police started shaking down the hop-joints so much.
1897, John Sanderson Christison, Crime and Criminals, page 58:
  Another female inmate of her abode told her its use would bring luck, so she spent a day in a "hop joint" smoking opium until night came.