life ‧ sav ‧ er /ˈlaɪfseɪvə $ -ər/ BrE AmE noun [countable]
1 . someone or something that helps you avoid a difficult or unpleasant situation:
A microwave oven can be a real lifesaver when you’re pressed for time.
2 . someone or something that prevents you from dying:
The seat belt is the biggest single lifesaver in cars.
3 . a ↑ lifeguard