Something that is bleak is gloomy and depressing. If it's raining and dark, you might describe the night as bleak. If you have looked for work and no one will hire you, you could describe your prospects as bleak.
If you and the ten people sharing your lifeboat have been adrift for ten days and are down to your last cracker, your situation is bleak. A near synonym is dismal. Bleak is from Middle English bleik, from Old Norse bleikr "white, pale." This word is related to the English word bleach.