Rocket (JP) is an item found in Super Mario Bros. 2. Like most other objects Mario needs to pull this out of the ground, it activates immediately and acts as a way for Mario and friends to get from one portion of level to the next acting like a door. It goes a certain height to where the character jumps out and then it blows up. There are only two Rockets in the whole game, in World 4 and World 7.
There are also rockets in Super Mario 3D World. After defeating Meowser in World Bowser, the Sprixie Princesses will build a Rocket to World Star in World 1. Additional Rockets are at the end of World Star and World Flower once those worlds have been completed.
Rockets also return in Super Mario Odyssey where Mario would capture a Rocket and will launch to a sky-themed level.