yeah. its a diss in the sense "player knock it off your not 2pac" cause pac stole that line from MJ but thats ok because he's 2pac, (kinda a weak diss if you ask me). Anyway the real phrase is spelled "Ma ma se, Ma ma sa, ma ma coo sa" just Google that line in quotes if your really interested in where it originates. Its just poetry. in the same sense as "la la lalalala" or "doe rae me fa....." (although doe rae me thing also doubles as scales"
again this doesn't mean anything it was just Micheal Jackson (i believe was first) trying to put to words the notes heard in that disco song i mentioned above. Critics also note it as one of the highlights of the thriller cd. So this is a very well known phrase by the Micheal Jackson era
download "Micheal Jackson - Wanna be startin something" thats where it all started
same question asked and answered by Yahoo! Answers:
http://answers.yahoo.com/question/index ... 046AAIecOh
MJ - Wanna be startin something
http://www.youtube.com/watch?v=8ml00fMJ9ok (bout 4 minutes in)