A "substantial portion" means a large or significant part of something. It refers to a significant amount or a considerable portion of a whole. Full definition
Meals are typically composed of substantial portions of protein, good fats, and veggies. (frugalgranola.com)
Everything is affordable and comes in substantial portions by beauty industry standards. (notetoselfblog.com)
With growing numbers of clients with substantial portions of their assets in qualified retirement plans, it is more important than ever to understand how these unique accounts can affect their estate plans. (edwardjones.com)