1. unable to be found or recovered
2. unable to find one's way or ascertain one's whereabouts
3. confused, bewildered, or helpless: he is lost in discussions of theory.
4. (sometimes foll by on) not utilized, noticed, or taken advantage of (by): rational arguments are lost on her.
5. no longer possessed or existing because of defeat, misfortune, or the passage of time: a lost art.
6. destroyed physically: the lost platoon.
7. (foll by to) no longer available or open (to)
8. (foll by to) insensible or impervious (to a sense of shame, justice, etc)
9. (foll by in) engrossed (in): he was lost in his book.
10. morally fallen: a lost woman.
11. (Theology) damned: a lost soul.
12. get lost (usually imperative) go away and stay away