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Amount of sleep which is needed for a person to look good when he or she gets up in the morning.
Cuddy: You look like hell! Are you sick?

House: I'm fine. I just didn't sleep last night. And here, you probably thought that 'beauty sleep' is just a woman's term. Sexist pig."
by sysonpyh July 02, 2009
Sleep necessary for good health, concentration etc.
Not now, I need my beauty sleep.
by The Return of Light Joker July 23, 2009