the policy or action of using vigorous campaigning to bring about political or social change.
"growing activism on the sustainability issue"
Protesting, campaigning, and pushing government bodies to change the world are powerful ways to be an activist. I do however think that there are many other ways of being an activist and it can move beyond that, though the dictionary seems to suggest the contrary.
Activism in it's technical definition is not necessarily available to all of us, be that because of accessibility issues, the possibility of death (certain political climates don't allow for it), or on a simpler note because it can take over one's life and we may not currently have the space for that. But, that doesn't mean we should simply leave it at that, activism can also come in the form of the choices we make in day-to-day life. Ultimately we need the rigorous, politically driven, physical kind of activism, but I would not want people to feel as though they cannot contribute to the discussion and growing movement around sustainability if that's not available to them.
Activism can come out in your approach to life, in the day to day actions and choices you make. Intentionally deciding to live your life a certain way in light of a current world issue is activism. It can be as obvious as using a massive tote bag with the word vegan across it, or as small as using your own container at a restaurant. These actions, small as they may seem, can start conversation and can have an impact on those around you. You are proudly showing the world what kind of earth you want to live on, and to me, that is pretty good activism too.