A regular succession of public conveyances plying between certain places; e.g. the Cunard line (of steamers), the White Star line. Originally U.S.

A line attached to a fixed point, such as an anchor, and used to help keep a boat stable and pointing in the desired direction when attempting to…

(a) the line on a vessel's hull which marks the level of the water when she is ballasted and rigged for sailing, but not laden or armed; (b) a line…

a transport line flying the flag of a specified country.