The experience of waking up in the middle of the night, and not being able to go back to sleep for a couple of hours or so. This usually leads to you doing things like checking Facebook, eating snacks and just generally doing what you'd do during the daytime, before going back to sleep like it never happened. The exact opposite of taking a nap, sometimes referred to as a 'reverse nap'. They are super inconvenient.
Emma: Hey, why were you posting something on Facebook at 5am last night?
Issie: Oh I was taking a wake.
Emma: Damn, I hate wakes. They're so inconvenient.