A momentary high voltage is a:

Too much voltage for a short period of time is a spike.

Too much voltage for a long period of time is a surge.

Not enough voltage for a short period of time is a sag or dip

Not enough voltage for a long period of time is brownout

A short power interruption is a fault

A long power interruption is a blackout

You MUST know all of the power issues above for the purpose of the exam.

From: HARRIS, Shon, All-In-One CISSP Certification Exam Guide, 3rd. Edition McGraw-Hill/Osborne, 2005, page 368.