Quit is the command to end the current game, by pressing Ctrl-q or *-q. This has the same effect as dying - you will not be able to resume play with that character! To merely end the current session and resume later, you must save the game instead.
Quitting will display the usual inventory and score screens, and the reason for game ending will be recorded as 'quit the game' in the high score table.
To prevent accidental quits, the player will be prompted to type in 'yes' to quit the game.