According to the dictionary, synergy has a simple definition:
“A synergy is where the whole is greater than the sum of its parts. In other words, when two or more people or organizations combine their efforts, they can accomplish more together than they can separately. They can get more done working together than they can working apart.”
Personally, when I think of synergy I think of strength.
Consider a wall of bricks stacked on top of one another 10 feet high with no mortar.
Push on the center and it will cave in.