1. seafarer. Sailor, mariner, salt, seaman, tar are terms for a person who leads a seafaring life. A sailor or seaman is one whose occupation is on board a ship at sea, especially a member of a ship's crew below the rank of petty officer: a sailor before the mast; an able-bodied seaman. Mariner is a term now found only in certain technical expressions: master mariner (captain in merchant service); mariner's compass (ordinary compass as used on ships); formerly used much as “sailor” or “seafaring man,” now the word seems elevated or quaint: Rime of the Ancient Mariner. Salt and tar are informal terms for old and experienced sailors: an old salt; a jolly tar.