From English - German Ding/FreeDict dictionary ver. 1.9-fd1:
stuning /stjˈuːnɪŋ/
fassungslos/sprachlos/bestürzt machend, völlig konsternierend, völlig frappierend
Synonyms: dazing, dumbfounding, nonplusing, numbing
see: stun sb., daze sb., dumbfound sb., nonplus sb., numb sb., stuned, dazed, dumbfounded, nonplused, numbed, be stunned, dumbfounded, nonplussed