If you're a heavy sleeper in the mornings, someone might have to jostle you awake. They might shake your shoulder, or shove you with a pillow, or even jump on your bed to jostle you all around. Get up!
When people are jostling with each other for something, or jostling against each other for something, they're both trying to get it for themselves, as if they're bumping each other out of the way. The players below are jostling for the ball. It means they're bumping into each other, both trying to grab the ball.
But you can jostle with someone without actually pushing or shoving each other; for example, you and your best friend might be jostling for first place in a spelling bee.
Often it's people who jostle for something, but it can also be things that jostle each other. On a busy street like this, all the signs and screens jostle for your attention! That means they seem to fight each other, shoving each other out of the way, so they can be the one to grab your attention.