Meaning: desperate, with no other options (definition).

Example: In a strange city and her wallet stolen, her back was against the wall.
Origins: expression from fighting. (Also, “back to the wall”). (Source.)

Rewrites: back against the bricks backside to sheet rock face to the fence facing six sides of the walls penned in by walls, fences, and borders no escape but a bottomless pit facing a ladder well shy of a climb to the top facing a hallway ending in a locked door
Discussion: What other words do you have for “wall” or “back”?