النوم الكامل
Deep or complete sleep.
Sleep is not itself proof that a particular discharge occurred. Yet deep sleep may prevent a person from monitoring whether ritual impurity arose. Because the occurrence of the underlying condition is not always knowable, the relevant juristic rule uses qualifying sleep as an outward proxy for that condition when assessing wudu.
Not every momentary doze is equivalent, and the proxy is not literally the same as a physical discharge. The doctrine assigns legal effect to a detectable circumstance where the underlying event may be hidden.