The word 'door knocker' is defined as a metal object attached to a door, which is used to knock on the door. However, there are several other synonyms for the word 'door knocker', including 'doorknob', 'handle', 'ring', 'pull', and 'bell'. However, these synonyms have slightly different meanings and uses. A 'doorknob' is used to turn and open a door, whereas a 'handle' is a metal bar or strap attached to the door for pulling it. 'Ring' refers to the sound when a person taps on the door, while 'pull' is used to grab and pull the door. Lastly, a 'bell' is an electric or mechanical device that is used to alert the homeowner of someone's presence at the door.