From Longman Dictionary of Contemporary Englishdoormatdoor‧mat /ˈdɔːmæt $ ˈdɔːr-/ noun [countable] 1 DHHa piece of material inside or outside a door for you to clean your shoes on2 informalTREAT/BEHAVE TOWARDS someone who lets other people treat them badly and never complains Don’t let him treat you like a doormat.
Examples from the Corpus
doormat• If you hadn't been a doormat you wouldn't have been trodden on - that's what doormats are for.• Make sure he doesn't treat you like a doormat.• A doormat for that bullying old harridan to wipe her feet on.• In a matter of seconds, I went from being the class doormat to class hero.• There was a letter on the front doormat bearing his name, manually typed.• Fiona was determined that she would be nobody's doormat.• Let him realise one thing: she might be poor, but she was nobody's doormat!• The key is under the doormat.treat ... like a doormat• You can't force him to act responsibly but you can make sure he doesn't treat you like a doormat. 