Lethargy

• Unnaturally sound sleep
• Very deep sleep
• Rip Van Winkle's state
• Profound sleep
• State of deep sleep

Wiktionary Word definitions in Wiktionary
n. an unnaturally deep sleep

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
Latin, "deep sleep, lethargy," from PIE *swep-os- , suffixed form of root *swep- (1) "to sleep" (see Somnus ).

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Sopor \So"por\, n. [L.] (Med.) Profound sleep from which a person can be roused only with difficulty.

Wikipedia Word definitions in Wikipedia
Sopor is a condition of abnormally deep sleep or a stupor from which it is difficult to rouse. It involves a profound depression of consciousness, which is manifested by drowsiness, while maintaining coordinated defensive reactions to stimuli such as pain, ...