>>7277132The "make your own meaning" definition. that was sticked to existentialism on this board isn't quite accurate. Nihilism is, in it's core, a form of existentialistic thought.
Existentialism in a movement, both in philosophy and literature, which places the experience of existing as the first and foremost in the human experience. Not our thought, not different definitions and values we are given, or any other idea that is floating around. In the nature of your existence you're an individual, that will live and parish. That you should consider in everything you do, and make it a starting point for your values and ideas. Many different conclusions can be derived from this approach, and the popular ones are, in fact, very different. Christian existentialists for instance, believed in god as the meaning for everything, and saw the moral values of christ as absolute and universal. None of that "do it yourself" approach here. Only certain existentialists (Kierkegaard, Sartre, etc.) really suggest the idea (and possibility) of forging your own meaning to your existence.
Nihilism, as a movement that evolved from existentialistic thought, comes to the conclusion that every single value we apply to the world is arbitrary, and originates in our (individual) experience of the world rathen than an absolut truth.
Therefore, it rejects any value previously applied to the world, and any chance of life having a meaning.
Hope the distinction is clear enough.