I. main ‧ stream 1 /ˈmeɪnstriːm/ BrE AmE noun
the mainstream the most usual ideas or methods, or the people who have these ideas or methods
the mainstream of
Environmental ideas have been absorbed into the mainstream of European politics.
Genet started as a rebel, but soon became part of the literary mainstream.
II. mainstream 2 BrE AmE adjective [only before noun]
accepted by or involving most people in a society:
Deaf children can often be included in mainstream education.
the mainstream political parties
III. mainstream 3 BrE AmE verb [transitive]
American English to include a child with physical or mental problems in an ordinary class
—mainstreaming noun [uncountable]