noun

1. the middle of a stream, where the current is strongest
2. the part of something considered to be the most active, productive, lively, busy, etc. the mainstream of life
3. a major or prevailing trend, as of thought, action, literature, or music
4. ☆ Jazz a style of playing that evolved in the 1950s, based on rhythmic and harmonic elements of swing modified slightly by those of bop

transitive verb

1. to cause to undergo mainstreaming
2. to bring into the mainstream, as of employment, the economy, or politics