To be unconscious or in a deep sleep. Likened to a boxer who has been knocked out. I didn't even hear you come in last night—I was so tired that I was out for the count as soon as my head hit the pillow. On his 21st birthday, Mike's friends gave him so much to drink that he was out for the count by 10 PM. The rowdy customer was out for the count when the bouncer punched him in the head.