The word ' substantial ' evolved over time to describe something of considerable size, amount, or importance. Its etymology reflects the concept of something having a solid and significant presence, emphasizing its substantial nature without directly delving into its meaning . SUBSTANTIAL meaning : 1. large in size, value, or importance: 2. relating to the main or most important things being…. Learn more. Learn the meaning of substantial as an adjective, with synonyms, examples, and pronunciation. Substantial can mean large, important, solid, real, or essential, depending on the context. Learn the meaning of substantial as an adjective to describe something large in amount, value or importance. See how to use it in sentences and compare it with synonyms and related words.