Definition of lost :
1. Hardened beyond sensibility or recovery; alienated; insensible; as, lost to shame; lost to all sense of honor.
2. Having wandered from, or unable to find, the way; bewildered; perplexed; as, a child lost in the woods; a stranger lost in London.
3. Not employed or enjoyed; thrown away; employed ineffectually; wasted; squandered; as, a lost day; a lost opportunity or benefit.
4. Not perceptible to the senses; no longer visible; as, an island lost in a fog; a person lost in a crowd.
5. Occupied with, or under the influence of, something, so as to be insensible of external things; as, to be lost in thought.
6. Parted with unwillingly or unintentionally; not to be found; missing; as, a lost book or sheep.
7. Parted with; no longer held or possessed; as, a lost limb; lost honor.
8. Ruined or destroyed, either physically or morally; past help or hope; as, a ship lost at sea; a woman lost to virtue; a lost soul.
bewildered, confounded, hidden, law, at sea, confused, illogical, wooly, dead, ruined, get out, scattered, forfeit, unredeemed, condemned, weak, get, feeble, unsaved, muddled, obscured, come back, straying, incomprehensible, absent, unrecoverable, new, baffled, wooly-minded, minus, leave, vanished, mislaid, lacking, addled, confiscate, begone, doomed, mazed, unprofitable, wandering, hopeless, live, seek, upset, befogged, disabled, foredoomed, without, garbled, reward, religion, unconnected, sickly, strayed, broken, wasted, stray, woolly-headed, thoughtful, astray, destroyed, uncomprehensible, disordered, anomic, deep in thought, fated, cast away, squandered, disconnected, missing, helpless, bemused, alienated, found, befuddled, incapacitated, ignorant, preoccupied, defunct, doubtful, woolly, costly, perplexed, invisible, muzzy, damned, missed, unoriented, disoriented, disjointed, mixed-up
failed (part of speech: verb)
forgotten (part of speech: adjective)
lost (part of speech: verb)
forgot (part of speech: verb)