doormat
A mat by a door for wiping dirty shoes.
A doormat is a mat placed by a door for people to wipe their shoes on before entering. It catches dirt, mud, and moisture so you don't track it inside. Most doormats are made of rough, durable materials that scrape the bottom of your shoes clean.
The word also describes a person who lets others treat them poorly without standing up for themselves. When someone acts like a doormat, they accept unfair treatment, always give in to others' demands, and rarely assert their own needs or opinions. If your friend constantly asks to copy your homework and you always say yes even though it bothers you, you might feel like you're being treated like a doormat.
A person being a doormat might agree to take blame for something they didn't do, or always volunteer for the worst jobs while others take advantage.
There's a difference between being considerate of others and letting others walk all over you. Knowing your boundaries and speaking up respectfully can help you avoid being treated that way.