Wiktionary
n. The first sleep of the night in a biphasic sleep pattern.
Wikipedia
Dead Sleep is a 1992 Australian horror film about a series of suspicious deaths that occur in a psychiatric ward. The cast includes Linda Blair (who played the possessed girl in The Exorcist), veteran Australian actor Tony Bonner and Vassy Costiopoulos. The film went straight to video.
Dead Sleep's British director Alec Mills is better known for a long career as a cameraman. Dead Sleep marked his second directing credit on a feature, following another horror film shot in Australia: Bloodmoon (1990).
Usage examples of "dead sleep".
Jacob fell into a dead sleep, at last, without having his arms round David, who paid the reckoning, took his bundle, and walked off.
Cries of children urging themselves upon their exhausted mothers who were locked in a dead sleep, too tired to uncover their breasts and give suck.
His last thoughts before he fell into a dead sleep had been about what he could tell them that might draw them off.
And another time when a pondering gale had kept him on the bridge for forty-eight consecutive hours, and a deputation of the deck hands raided him in the chart-house on the supposition that exhaustion would have laid him out in a dead sleep, he woke before their fingers touched him, broke the jaw of one with a camp-stool, and so maltreated the others with the same weapon, that they were glad enough to run away even with the exasperating knowledge that they left their taskmaster undamaged behind them.