To have an incredibly large pile of shit placed in front of your door. It can be done as a form of retaliation against a perceived slight, or simply because someone doesn't like you.
Origin: Flatbush, Brooklyn, where this form of justice is carried out on an alarmingly regular basis.
After Cynthia told her neighbor Ray to keep the noise down, she opened the door the following morning to see she had been Flatbushed and she started gagging on the smell.
When you go to a pub / restaurant / flat to meet up with someone and find yourself unexpectedly meeting their whole family.
Christine was thinking about dropping her new boyfriend / fuckbuddy Roger. When she arrived at the pub for a beer with him, she found he had invited his family to meet her. Christine had been fambushed.