That's not how dictionaries work. The definition points at a meaning: it doesn't construct it, mathematics-style.
Activism is where you take action to change something specific and significant, relative to the counterfactual where you did not take such action. (It also includes failed attempts at the same.)
If – say – there were strong social taboos against using the letter "e", and by using them in your comment you aimed to erode them, then yes, pressing "submit" would be activism. The same if you were coming out publicly, with the aim to make it easier for others to do so. Wearing clothes can be activism. There's no reason that lawsuits shouldn't qualify, if their goal is to create a better world.
"Create a better world" isn't a necessary condition for being activism.
> A long time ago, I was in Burma. My friends and I were working for the local government. They were trying to buy the loyalty of tribal leaders by bribing them with precious stones, but their caravans were being raided in a forest north of Rangoon by a bandit. So we went looking for the stones, but in six months, we never met anyone who traded with him. One day, I saw a child playing with a ruby the size of a tangerine. The bandit had been throwing them away.
> So why steal them? Well, because he thought it was good sport. Because some men aren't looking for anything logical, like money. They can't be bought, bullied, reasoned or negotiated with. Some men just want to watch the world burn.
— The Dark Knight, by Christopher Nolan and Jonathan Nolan
Activism is where you take action to change something specific and significant, relative to the counterfactual where you did not take such action. (It also includes failed attempts at the same.)
If – say – there were strong social taboos against using the letter "e", and by using them in your comment you aimed to erode them, then yes, pressing "submit" would be activism. The same if you were coming out publicly, with the aim to make it easier for others to do so. Wearing clothes can be activism. There's no reason that lawsuits shouldn't qualify, if their goal is to create a better world.
"Create a better world" isn't a necessary condition for being activism.
> A long time ago, I was in Burma. My friends and I were working for the local government. They were trying to buy the loyalty of tribal leaders by bribing them with precious stones, but their caravans were being raided in a forest north of Rangoon by a bandit. So we went looking for the stones, but in six months, we never met anyone who traded with him. One day, I saw a child playing with a ruby the size of a tangerine. The bandit had been throwing them away.
> So why steal them? Well, because he thought it was good sport. Because some men aren't looking for anything logical, like money. They can't be bought, bullied, reasoned or negotiated with. Some men just want to watch the world burn.
— The Dark Knight, by Christopher Nolan and Jonathan Nolan