Enter upon Definition 1 of 3Pro Tip 1/3Project Milestones Used when initiating significant stages within a project or plan. With the design complete, we'll enter upon the construction phase. Pro Tip 2/3Not Instantaneous The process following 'enter upon' often takes time to develop, not happening suddenly. She'll enter upon a year of travel and discovery. Pro Tip 3/3Anticipation Indicates moving forward with a sense of expectation for what comes next. They will enter upon negotiations with hope for success.