If its the Wild Beast at PCW, then I know what you're talking about. I call it the "ouch turn".
For me, its any time you get stuck on the lift hill. I know it doesn't happen often, but when it does, its a weird feeling. I remember getting stuck on Dueling Dragons: Ice a few years back and my sister was freaking out.
One time on dragon fire (pcw) the train was almost to the top of the hill when for no reason the lift chain shut off. i was up there for 20 minutes. till this day nobody knows why the chain shut off