Grenade jumping

In first-person shooter games, rocket jumping is the technique of using the explosion of a rocket launcher combined with a jump. The aim of this technique is to reach new heights and distances. Although the origin of rocket jumping is unclear, its use dates back at least to play in Quake. The biggest downside of rocket jumping is that it usually injures the player, either from the blast damage or fall damage. This effect makes the technique less useful in games where the damage from the blast, fall, or both is high. The technique is used especially in advanced/competitive play where it is used in order gain quick bursts of speed, reach normally unobtainable heights, secure positional advantages, or in speedrunning.

While rocket jumping was first seen in Doom, the technique became a core mechanic in Quake, taking the technique to literal new heights. By exploiting the various quirks of the Quake engine, many advanced movement techniques were spawned: such as circle jumping, strafing, bunny hopping, and of course explosive jumping. The community quickly became accustomed to using these various methods of gaining speed, and so was born the first speedrunning community. Rocket jumping was kept as an intentional mechanic for the leading games in the Quake series. In Quake III: Arena some of the computer-controlled opponents use rocket jumps.

In the game, Team Fortress 2 (2007), players could use the explosive knockback of a Soldier's rockets to rocket jump. Rocket jumping usually costs players around 40 health (1/5th of Soldier's total hp). As the Soldier class has a 40% resistance to his own rockets that do not damage other players. In addition, damage boosters, such as critical hits or mini-critical hits do not give extra self knockback or self damage to the Soldier, so they will not propel him further. Items such as the Rocket Jumper, Liberty Launcher, or Gunboats can reduce self damage from rocket jumping.

...
Wikipedia