on the line adverb (or adjective) 1. a.: on a level with the eye of a spectator — used of the arrangement of a picture in an exhibition b.: in full view and at hazard < put his future on the line when he backed this policy > 2.: on the border between two categories of a classification 3.: immediately : without delay < paid cash on the line > 4.: into prostitution < she lost her job and went on the line >