The phrase "momentous week" refers to a very important, significant and impactful week with important events or decisions taking place. Full definition
Coming on the heels of Norton Rose's merger with / acquisition of firms in Canada and South Africa, it amounts to one of the most momentous weeks in recent marketplace memory. (law21.ca)
This is a momentous week, with President Obama, President Xi Jiping, and the Pope addressing the United Nations General Assembly. (inc.com)
«This was a momentous week in history of Barclays.» (politics.co.uk)