Players can reach much higher speeds by repeatedly jumping while running in any direction, with the speed increasing with each jump. Used for the speed benefit as well as to make targeting harder for the opponents.
Alternate names: Strafe-jumping
Name variations: Bunny-hopping, Strafe jumping
The first video game about Bunny hopping was released in 1996.
Usually this is possible only because of unaddressed bug in physics simulation (however limited it is), but can occasionally be intentional (or intentionally left unfixed).
Strafe-jumping is a more potent jump trick possible in some games (most notably Quake 3), but is occasionally used interchangeably with bunny hopping. The effect is still the same.