The feeling which occurs after one has stayed up past his sleep cycle such that the body has abandoned its "
go to sleep" feeling and has
shifted into a light buzz.
It is comparable to the
lingering buzz that remains in the morning after a night of drinking, because the body is rather awake yet clearly not fully sober.
KATE: John,
go to bed. Aren't you
sleepy? You were
dozing off at your desk a few hours ago.
JOHN: Yeah, but the sleepy part of my cycle is over. It's back into awake mode, so I'm lanked now.