Fusion/ˈfjuːʒn/ Definition 1 of 5Pro Tip 1/3Conceptual Unity Used to describe a process where separate elements become one with new properties. The fusion of traditional and modern designs is impressive. Pro Tip 2/3Not Always Physical Fusion can refer to abstract concepts coming together, not just tangible items. The fusion of ideas from different employees led to the new strategy. Pro Tip 3/3Not Always Physical Fusion can refer to abstract concepts coming together, not just tangible items. The fusion of ideas from different employees led to the new strategy.