from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A naive idealist who supports philanthropic or humanitarian causes or reforms.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. One who advocates or performs what they believe to be the morally superior course of action, even in the face of overwhelming experience or factual evidence that its effect is only irrelevant or harmful.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. someone devoted to the promotion of human welfare and to social reforms
From do + good + -er. (Wiktionary)