A momentary power outage is a fault.
Power Excess Spike –> Too much voltage for a short period of time. Surge –> Too much voltage for a long period of time.
Power Loss Fault –> A momentary power outage. Blackout –> A long power interruption.
Power Degradation Sag or Dip –> A momentary low voltage. Brownout –> A prolonged power supply that is below normal voltage.
Reference(s) used for this question: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, 3rd. Edition McGraw-Hill/Osborne, 2005, page 368. and https://en.wikipedia.org/wiki/Power_quality