The concert was cut off due to a sudden power outage.

cut off 是由动词 cut（切断）和副词 off（离开）组成的短语动词，意思是"中断、切断"。 power outage 是由名词 power（电力）和名词 outage（中断）组成的复合名词，指"电力供应中断"，即"断电"。