Top Definition
The opposite of 'mainstream'. Applies to music (modern and older), books, hobbies, movies, etc.

The 'Is It Mainstream Music?' Test: Does this song/band play on more than three radio stations? Yes- Most likely main. No- Most likely sub.
Miley Cyrus and Jay-Z? Mainstream. Freezepop? Substream.
by Unexist May 16, 2010

Free Daily Email

Type your email address below to get our free Urban Word of the Day every morning!

Emails are sent from We'll never spam you.