There are two meaning of Hacker:
1. a person or thing that hacks computer technology or programming; they are known as computer experts or enthusiast.
2. a person who circumvents security and breaks into a network, computer, file etc.
And for the hacktivism, it is also meaning as "Hacker". Hacktivism is according to information security researcher. It is the practice of gaining unauthorized access to a computer system and carrying out various disruptive actions as a means of achieving political or social goals.
These are the lists that happened last time:
Definition of Hacker
Definition of Hacktivism
Brief historical breakdown on the rise of hacktivism