[transitive] lose something/somebody to have something/somebody taken away from you as a result of an accident, getting old, dying, etc. She lost a leg in a car crash. to lose your hair/teeth (= as a result of getting old) He's lost his job. Some families lost everything (= all they owned) in the flood. They lost both their sons (= they were killed) in the war. The ship was lost at sea (= it sank). Many people lost their lives (= were killed).