lifesaver
nounUK /ˈlaɪfˌseɪvə/
US /ˈlaɪfˌseɪvər/
A lifesaver is a person or thing that saves someone from danger.
The lifeguard was a lifesaver when the boy got caught in the waves.
OTHER MEANINGS
2. A ring-shaped float used to keep a person from sinking in water.
She threw the lifesaver to the swimmer in the pool.
3. A sweet ring-shaped candy with a hole in the middle.
He shared a pack of lifesavers with his friends.
4. Something that helps you out of a difficult situation.
Your spare key was a lifesaver when I locked myself out.