"Matter moment" is an expression that refers to a significant moment or event. There are many synonyms that can be used in place of this phrase, such as a turning point, pivotal moment, critical juncture, or defining moment. Other options include a watershed moment, a momentous occasion, a game-changer, or a milestone. These words all convey a sense of importance and gravity, indicating that the moment in question is one that has a significant impact on the future. Each of these terms can be useful when trying to describe moments of significance in personal, professional, or historical contexts.