Lost is the past tense and past participle of the verb "lose".
Common meanings of lost include:
1. Unable to find one's way; not knowing one's whereabouts
2. That cannot be found or recovered
3. Having gone astray or missed the way
4. Not used to good purpose, wasted
5. No longer possessed or existing
6. Ruined or destroyed physically or morally
7. Overwhelmed with strong emotion
8. (in sports) Having been defeated