look up any word, like fleek:
 
2.
Horrible song by the gay singer Hilary Duff.
Also, something said when something is out of style
Kung-Fu Jesus is so yesterday!
by Ka August 29, 2004
 
1.
Something which was once popular, until it went uber-mainstream, and has now become passé
Grunge is so yesterday, get over it.
by Kung-Fu Jesus April 15, 2004