activist

[ˈæktɪvɪst]

Definition:
1. A person who works to bring about political or social changes by campaigning in public or working for an organization.

'activist' example sentence:

1. Activist investors rarely bother to target Japanese firms-and are normally sent packing if they do.
2. The question now is whether Mr. Kan, a plain-spoken former civic activist, can further defy precedent by lasting more than a year in office.
3. This year, however, Japanese managers faced an even more menacing threat: activist shareholders.
4. He is now a gender activist and senior manager at the community organisation the Olive Leaf Foundation.
5. I will always be politically active, but will never be a political activist.
6. This is a place for government to play an activist role: opening monopoly markets to competition.
7. He's been a trade union activist for many years.
8. I am an information activist.
9. He's a gay rights activist.
10. He has always been a political activist.
11. The free software activist will say, "your program is very attractive, but I value my freedom more. so I reject your program."
12. She chronicled her quest on her blog, Not an Activist.
13. The police say they suspect the attack was carried out by animal rights activists.