Waterproof coats that protect you from the rain.
Slickers are good to have when it's raining because they keep you dry.
Examples:
She wears her yellow slickers when it rains.
Do you have your slickers with you today?
I put on my slickers before going outside.
His red slickers make him look like a big tomato.
I need my slickers because it's raining cats and dogs!
The bright yellow slickers are easy to see in the dark.