malfunction
verb [ I ]
 /ˌmælˈfʌŋkʃən/ ukusif a machine or system malfunctions, it stops working normally: 
 The system is designed to stop computers getting too hot and malfunctioning.
 malfunction
noun [ C or U ]
 /ˌmælˈfʌŋkʃən/ ukusa situation in which a machine or system stops working normally: 
 Investigators believe the spillage was caused by a malfunction at the plant in the immediate aftermath of the earth tremor.
 a technical/mechanical/electrical malfunction
 a computer/equipment/system(s) malfunction