Adjective

1. Cast adrift or ashore; marooned.

   After the mutiny, the castaway ship's officers suffered a month at sea in the lifeboat.

2. Shipwrecked.

   The storm left them castaway on an uninhabited island.

Noun

1. A shipwrecked sailor.

   Robinson Crusoe was a famous fictional castaway.

2. A discarded person or thing.

   This old coat was a castaway in someone's trash.

3. An outcast; someone cast out of a group or society.

   These homeless people are society's castaways.