the mainstream [singular] the ideas and opinions that are thought to be normal because they are shared by most people; the people whose ideas and opinions are most accepted His radical views place him outside the mainstream of American politics. He was never part of the literary mainstream as a writer. See related entries: Describing musicExtra examples He drifted out of the mainstream of society. He was in the mainstream of British contemporary music. These teachers have been cut off from the mainstream of educational activity. This style of drama is not part of the cultural mainstream. This technology was designed for specialists but is now starting to move into the mainstream.