Gossip; particularly where information gets around that is not supposed to. "Loose lips sink ships" was a famous saying in World War I.
LOOPWZ - LOOPZ - LOOR - LOOS - LOOSE - LOP - LOP-L - LOP-P - LOP-V - LOPA
"LOOSE LIPS." Abbreviations.com. STANDS4 LLC, 2015. Web. 22 May 2015. <http://www.abbreviations.com/LOOSE%20LIPS>.