Wife: You took a long time in the bathroom to get ready this morning.
Husband: I was real tired and had trouble waking up. I fell asleep in the shower.
A sex position, but also a sex CONCEPT. The idea is that you ask the lady until you're good and sleeping and then to get it on with you real careful like.
This term describes the nightly experience of those unfortunate schmucks who just absolutely cannot fucking fall asleep, no matter how much thrashing around in bed they do or how much ruminating over past mistakes they indulge in. Instead of falling asleep, an insomniac is simply failing asleep.
Alice: "Wow, you look like hell"
Bob: "<mumble> last night I was failing asleep and couldn't stop thinking about some shit from middle school when I got my bike stolen"
Person 1: Yeah, nothing could wake you up this morning. You were dead asleep.
Person 2: Didn't you throw water on me? When I woke up I was soaked.
Person 1: As I said, you were dead asleep. You didn't move an inch when I threw water on you.