When something moves close to a planet or other object in space so that it can change its path and speed.
This is a special word used in science and space things.
Examples:
The spaceship will swingby the moon to get faster.
The comet did a swingby of the sun.
The satellite did a swingby of Jupiter.
The bird did a swingby of the tree and then flew away.
The car did a swingby of the gas station to pick up some snacks.
The spaceship did a swingby of the planet and then went really fast.