Howl (雄叫び) is a supportive technique used by Great Apes and certain other fighters.
The user howls loudly, which magnifies the users power, putting them straight into Max Power mode and increasing their physical attributes. However, once the power wears out, the user will have a hard time gaining back their ki, making them take a much longer amount of time to be able to use ki-based attacks.
Several other giant characters use it in battle in the Dragon Ball Z anime and movies.
In Dragon Ball GT, Vegeta uses it after turning into a Great Ape.
Video Game Appearances
Howl was named and is used in the Budokai Tenkaichi series and Dragon Ball Heroes. In terms of appearance, it is nearly the same as Full Power, except with a howl and sometimes a monkey-like pounding on the chest. It is also very similar to Full Power in that it initiates Max Power mode, albeit it uses two Blast Stocks to execute. Mr. Satan and Android 8 are the only non-giant character to use the technique in the Tenkaichi game; Mr. Satan's version is called Champion Style?! in Dragon Ball Z: Budokai Tenkaichi 3 and Number One! in Dragon Ball: Zenkai Battle. The Bear Thief uses the technique to increase his defense in Dragon Ball: Revenge of King Piccolo.
In Dragon Ball Xenoverse, it appears listed in Great Ape Vegeta's skillset and Golden Great Ape Baby's skillset when fought in the game's story. It is also listed in Great Ape Bardock's and Great Ape Nappa's skillset when scanned in search view when they are fought during Parallel Quest 52: "Great Ape Festival". In this game, it is an Evasive Skill used by non-playable Great Ape boss characters.