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2.
A record or song so irritating, grating or terrible that it is nearly guaranteed to clear out any group of people from any given space.
Lamont put on Lou Reed's Metal Machine Music, the ultimate party ender, when he'd had enough of pretending he liked these people in his house.
by Andrew Mudd June 19, 2007
 
1.
Police.
The cops came and ended the party.

The other definition of party ender is lame.
by jebusjoe March 23, 2011