Definitions
1.AdjectiveUsed or accepted broadly rather than by small portions of population, market, scientific community, etc."They often carry stories you won't find in the mainstream media."
2.NounThe principal current in a flow, such as a river or flow of air
3.NounThat which is common; the norm."ideas outside of the mainstream"
4.VerbTo popularize, to normalize, to render mainstream.
5.VerbTo become mainstream.
6.VerbTo educate (a disabled student) together with non-disabled students.