1. A tactic utilized by the Japanese Samurai and later the Imperial Japanese Army from the feudal era up to the end of World War 2.
Where when the enemy has weakened their unit to the point where it has no option but to retreat or surrender, they issue a "Banzai" charge in which they rush head first into the enemy and attempt to engage in close combat, usually with bayonets and swords.
Typically an act of self sacrifice rather then to dishonor their army and country by surrendering to the enemy, an action related to Bushido.
It is traditional to scream the word before attacking followed by a non-linguistic war cry.
2. Slang in video games for a hopeless rush against the enemy, often without any Japanese or Bushido affiliation.
1. "We've got both flanks locked, they gotta retreat sooner or later!"
"Shit, banzai charge! Fire at will!"
2. Damn man you banzai'd bad on that one.