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1.
Something that is so mainstream that pretty much everyone likes it and it becomes lame for that reason.
1. Dude, did you listen to Green Day? That's so lamestream.
2. I didn't want to be lamestream so I started listening to screamo.
by dave "pelirrojo" rogus November 18, 2007
 
2.
A term hipsters use to define something that tries to be hipster and fails by still being mainstream.
Hipster One: Did you see that girl wearing fake glasses?
Hipster Two: Yeah, she's being lamestream.
by IceOfWaterflock May 29, 2013
 
3.
Adj - A creative work that achieves mainstream popularity by trying to appeal to everyone, thus sacrificing the originality that made older fans first fall in love with said work.

See also: Sell Out
Carlos Santana became lamestream when he collaborated with bland pop artists on the album "Shaman".
by Normal1515 September 07, 2009
 
4.
Things that people participate in or go to because they think it will make them look hip.
Rob: Are you going to Lollapalooza on Friday?

Burt: Dude, Lollapalooza is SO Lamestream!
by Burt Maass March 21, 2008