sleep 
(slēp)
(slēp)n.
1.
a. A natural periodic state of rest for the mind and body, in which the eyes usually close and consciousness is completely or partially lost, so that there is a decrease in bodily movement and responsiveness to external stimuli. During sleep the brain in humans and other mammals undergoes a characteristic cycle of brain-wave activity that includes intervals of dreaming.
b. A period of this form of rest.
c. A state of inactivity resembling or suggesting sleep; unconsciousness, dormancy, hibernation, or death.
d. A state in which a computer shuts off or reduces power to its peripherals (such as the display or memory) in order to save energy during periods of inactivity.
2. Botany The folding together of leaflets or petals at night or in the absence of light.
3. A crust of dried tears or mucus normally forming around the inner rim of the eye during sleep.
v. slept (slĕpt), sleep·ing, sleeps
v.intr.
1. To be in the state of sleep or to fall asleep.
2. To be in a condition resembling sleep.
v.tr.
Phrasal Verbs: 1. To pass or get rid of by sleeping: slept away the day; went home to sleep off the headache.
2. To provide sleeping accommodations for: This tent sleeps three comfortably.
sleep around Informal
To have sexual relations with a number of different partners in casual encounters.
sleep in
1. To sleep at one's place of employment: a butler and a chauffeur who sleep in.
2.
a. To oversleep: I missed the morning train because I slept in.
b. To sleep late on purpose: After this week's work, I will sleep in on Saturday.
sleep on
To think about (something) overnight before deciding.
sleep out
1. To sleep at one's own home, not at one's place of employment.
2. To sleep away from one's home.
sleep over
To spend the night as a guest in another's home.
sleep together
To have sexual relations.
sleep with
Idiom: To have sexual relations with.
sleep like a log/rock
To sleep very deeply.
[Middle English slepe, from Old English slǣp; see slēb- in the Appendix of Indo-European roots.]