When rain scuds, it moves quickly and is blown by the wind. Scuds are also small, fast-moving clouds.
When rain scuds, it usually means the weather is changing and it might get stormy. Small, fast-moving clouds can make the sky look interesting.
Examples:
The rain scuds across the fields.
I saw scuds in the sky when the wind was strong.
When the rain scuds, it makes everything wet.
The scuds in the sky look like little fluffy animals running away.
The scuds raced across the sky like they were in a hurry.
The rain scuds so fast, it's like it's playing tag with the wind.