sleepless

Concise Oxford English Dictionary © 2008 Oxford University Press:
sleep/sliːp/

▶noun

• 1 a regularly recurring condition of body and mind in which the nervous system is inactive, the eyes closed, the postural muscles relaxed, and consciousness practically suspended.

• 2 a gummy secretion found in the corners of the eyes after sleep.

▶verb (past and past part. slept /slɛpt/)

• 1 be in a state of sleep.

  ■ (sleep something off) recover from something by going to sleep.

  ■ (sleep in) remain asleep or in bed later than usual in the morning.

• 2 provide (a specified number of people) with beds or bedrooms.

• 3 (sleep together/with) have sex or be involved in a sexual relationship.

  ■ (sleep around) have many casual sexual partners.

– phrases
put someone to sleep make someone unconscious with drugs or anaesthetic.
put something to sleep kill an animal painlessly.
sleep like a log (or top) sleep very soundly.

– derivatives
sleepless adjective,
sleeplessly adverb,
sleeplessness noun.

– origin OE slēp, slǣp (n.), slēpan, slǣpan (v.), of Gmc origin.