The term "substantial majority" refers to a large portion or number of people who support, agree with, or participate in something. It is generally used when describing an overwhelming amount of individuals that share similar opinions or take part in a particular activity. The exact percentage varies depending on the context and can range from 51% to 80% or more. In essence, it means that a substantial majority represents a large group of people who have a strong opinion or interest in something, making it an important consideration when making decisions or taking actions.