Some of the more drastic maneuvers employed by fighter planes involve deliberately induced stalls.
A stall occurs when an aircraft’s forward motion is insufficient for the wings to generate lift. The plane literally starts falling from the sky. Pilots recover by pushing the nose down into a dive, gaining enough speed for the wings to work. Sometimes stall happens when the plane tries to climb too steeply, causing the plane both to lose speed fighting gravity and also, because the wings present their underside instead of the leading edge to the air, prevent the airfoil effect from functioning and generating lift.
A stall may occur in a single wing, under certain maneuvers, causing the wing to drop and causing a sudden roll turning the plane upside down. This happens at low speed, usually in very tight turns. It is normally regarded as highly undesirable.
Some ace pilots like to do what is called a snap roll by pulling up then applying strong rudder, usually to the left. Pulling up brings the plane to the brink of stall. Using the rudder swings the plane (in this case) left, slowing the left wing past the stall point, causing that wing to fall suddenly and flipping the plane upside down and into a dive! And usually changing direction to run in the opposite direction it had been going.
Not all planes are suited to this maneuver because most will spin out of control. Japanese fighters on the other hand were noted for their easy recovery from violent stalls, especially the Ki-43 Hayabusa or Oscar. Therefore we find frequent mentions of the Hayabusa aces performing these wild snap rolls to throw off Allied attackers in pursuit. The jolting change of direction is extremely hard to follow if the attacking plane does not have the same level of maneuverability.