night terror

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An episode of nighttime awakening occurring in children, accompanied by intense fear and agitation and not recalled after awakening.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun pathology A sleeping disorder, where sleep is interrupted by anxiety, panic or screaming.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun an emotional episode (usually in young children) in which the person awakens in terror with feelings of anxiety and fear but is unable to remember any incident that might have provoked those feelings