Wiktionary
n. The cumulative effect of not getting enough sleep.
Wikipedia
Sleep debt or sleep deficit is the cumulative effect of not getting enough sleep. A large sleep debt may lead to mental or physical fatigue.
There are two kinds of sleep debt, the results of partial sleep deprivation and total sleep deprivation. Partial sleep deprivation occurs when a person or a lab animal sleeps too little for several days or weeks. Total sleep deprivation means being kept awake for at least 24 hours. There is debate in the scientific community over the specifics of sleep debt, and it is not considered to be a disorder.
Usage examples of "sleep debt".
Now, without electronic reveille electrically juicing up every fiber of his being, not to mention his body, at some repulsive early hour of the morning, he found that he could drift in the restful pools of somnolence for delirious long stretches, and so for awhile he did just that, putting paid to his sleep debt.
He had a sleep debt of at least a month by now, and it didn't look like he'd be catching up on it anytime soon.