1. gathering together or accumulating a large quantity of something over time
Usage: present participle of ‘amass’

Examples

• She has been amassing a collection of rare books for decades.
• The company is amassing data on customer preferences.
• He spent years amassing wealth through smart investments.
• The storm clouds were amassing on the horizon.
• The general was amassing troops near the border.
• They are amassing evidence for the court case.