A zero-g stall is a roller coaster inversion that the track rotates 180 degrees, while traveling uphill - fully inverting riders. The track then levels out and while travelling downwards, the track rotates 180 degrees again but in the opposite direction.
The element has been featured on twelve roller coasters, most built by Rocky Mountain Construction:
The Top Gun stall is very similar to the zero-g stall, the only difference being that it is only featured on dueling or racing roller coasters in which one track does a zero-g stall over the other track.
.htm Zero-g stall] on the Roller Coaster DataBase.