The phrase "major impact" refers to a significant, powerful or substantial influence that something has on a particular situation. It implies an effect that is considerable and noteworthy, capable of causing changes or alterations in circumstances, conditions or outcomes. The term can be used positively or negatively depending on the context - for example, it could refer to a positive change brought about by an innovation, discovery or event; or conversely, it could describe a negative impact such as damage, harm or destruction caused by natural disasters, accidents or human actions. Overall, "major impact" signifies something that has a profound and substantial effect on the matter at hand.