180 is a stunt in which the player during mid-air simply spins his/her car to the other direction or in other words, to spin half way, thus becoming the origin of the word. Although the stunt's purpose is rather limitied, it is still quite useful for strategies.
180 is quite useful for Wasting and strategies, though it yields very little amounts of Power. Most players usually go for higher power-gaining stunts, such as the 360 or 720. The stunt itself is extremely unrecommended for Racing, and thus should be limited at all costs.
This stunt results in 2-9% power gained after.
Every car can do this, if by going off a ramp. The same result it usually much harder to achieve if ramming (or being rammed by) another car, as it was simply cause either car to be pushed back.