MP3J 

a DJ who jockeys MP3s instead of disks.

"Yo did you go to the party at the barn last night?"
"Yea man, Brett is an ill MP3J"

MP3J by jpjpjp December 23, 2008

MP3J 

A DJ that plays exclusively from their laptop, iPod, or other electronic device.

Why is that MP3J calling himself a DJ, doesn't he know that DJ stands for Disc Jockey? Ya gotta play the wax!!

MP3J by rockin*Cat December 31, 2008

MP3J 

Some cat who's either clearly not into hip-hop, buying records or is just a lazy bolix. Quite similiar to a DJ except with MP3s.

"Man, That MP3J was playing some pretty snip beatz last night and she was also a total lasher", recalled Phadraig.

MP3J by Jonny Tennant December 12, 2005

Mp3j 

A music jockey who specializes in the presentation, mashing up, or other performance of electronically recorded files. Said jockeys may use prerecorded vinyl, cd or remixes from any source media, whether by themselves or others.

"That Mp3j really killed with that remix of the Stones and Beyonce. I can't believe he blended in Green Day and Bob Marley!"

Mp3j by Franklin In San Diego March 24, 2010