Vine Whip is Ivysaur's Up Special Move. Only seen in a screenshot, it appears that a vine extends upward from Ivysaur's flower in order to do a Tether Recovery. Ivysaur will also gain a small amount of upwards distance. When Ivysaur is on the ground, Vine Whip is used as an actual whip, like Sheik's Chain. Unfortunately, Ivysaur can easily be edgehogged while attempting to use the Vine Whip to recover.
Origins
In the Pokémon games, Vine Whip is a fairly standard grass type move. It is very frequently seen being used by Ivysaur and its evolutions in the anime.