Diss derives from the word disrespect and it is a part of a hip-hop culture. It refers to the situation when two rappers are verbally fighting with each other, putting their offensive sentences into their records.
I make disses about different Polish artists, not known personally to me, to intrigue them and to establish contact with them. Reactions of recipients to these unusual messages were very various. One of the artists dissed me back.
for more disses and info: ohkrzysiu.wordpress.com/2013/09/26/diss/