A victory pose is a short animation that any character does after winning a match while the losers stand in the background or in a separate window, applauding politely. Typically, every character will have three different poses that can be performed at the end of a match by holding down a certain button, which the DOJO!! claims is based upon the taunt being used by the character at the time, if any.
While a majority of characters will applaud for the victor, there exist some exceptions. In Super Smash Bros., Jigglypuff doesn't clap and instead just moves its head to the right and does nothing else, (But in Super Smash Bros. Melee onwards, it moves its head left and right without stopping) probably because its hands are too short to clap with. The Ice Climbers also don't clap and instead cry while wiping their faces, referencing the screen seen when failing a bonus stage in Ice Climber. Mewtwo simply stands with its arms crossed, looking away in disappointment. Diddy Kong takes off his cap and looks down at the ground with a confused expression on his face, scratching his head, which is a reference to his defeated pose from Donkey Kong Country games after losing in a bonus game room, though this is in Brawl only, as he does clap in Super Smash Bros. for Nintendo 3DS and Wii U. Wario will cease clapping every few seconds to open his mouth and call out towards the victor. And the Pokémon Trainer will pull his hat down, covering his face with his hand, and hang his head in disappointment while the last Pokémon he had out when the match ended applauds instead. Characters do not clap on the results screen in Super Smash Bros. for Nintendo 3DS or in team battles in either version of both versions of Super Smash Bros 4., although they still clap in the 'No Contest' screen.
In Melee, As soon as the match ends players can hold X or Y (or A and B for characters with more than two victory poses) to select which victory pose their character performs, that is if their character won the match. Similarly in Brawl, players can choose which victory pose is used at the end of a match by holding the "B" "X" or "Y" buttons on the GameCube controller at the end of a match until reaching the result screen.