not paying attention to a situation, so that something bad happens:
Several publishers were asleep at the switch, and missed the book's potential.
➔ go to sleep
at sleep2 (3) ➔ see usage notesleep1WORD CHOICE: WORD CHOICE: sleep, asleepYou usually use be asleeprather than 'be sleeping'• Her parents were already asleep (NOT already slept/were sleeping).The verb sleepis used when you are giving more information, for example about how long someone sleeps or where they sleep• The baby sleeps for 12 hours. • He slept in the car.You usually say fall asleep, not 'start sleeping'• Some students fall asleep (NOT start sleeping/start to sleep) at their desks.!! Do not say 'feel asleep'. You can also say someone goes to sleep, especially when they are in bed and want to sleep• I turned the light out and went to sleep.You use get to sleepwhen someone has difficulty falling asleep• It took me hours to get to sleep. ➔ See alsosleep
Definition from the Longman Dictionary of Contemporary English Advanced Learner's Dictionary.