IPA: /ˈfɜːrðər/
KK: /ˈfɜrðər/
A person who helps to promote or advance something, such as an idea or cause.
She is a furtherer of environmental awareness in her community.
Furtherer → It is formed from "further" (from Old English "furðor", meaning more distant or additional) and "-er" (meaning a person who). A furtherer is a person who promotes or advances something further.
Think of someone who helps to make something 'more' ('further') or 'additional' — the '-er' indicates that this person is actively involved in that process.