Longman Dictionary of Contemporary English - mainstream

~1 n 1 the mainstream of the most usual way of thinking about something or doing something  (Environmental ideas have been absorbed into the mainstream of European politics.) 2 the mainstream the people whose ideas about a subject are shared by most people and regarded as normal  (Genet started as a rebel, but soon became part of the literary mainstream.) - mainstream adj  (mainstream economic theory) ~2 v AmE to include a child with physical or mental problems in an ordinary class