IPA: //ˈæltruɪst//
KK: /ˈæltruɪst/
A person who cares about the well-being of others and acts to help them, often putting their needs before their own.
As an altruist, she dedicated her life to helping those in need.
Altruist is derived from "altru" (from French "altruisme", meaning other) and the suffix "-ist" (meaning one who practices or is concerned with). The word describes a person who is concerned with the welfare of others, emphasizing selflessness and generosity.
Think of someone who is focused on the 'other' ('altru') and is dedicated to helping them — that's what an altruist does.