看情况:
totally a nightmare = very frustrating (挫折) = very difficult = very annoying
我举几个例子好了:
Driving in heavy traffic is a total nightmare. = Driving in heavy traffic is very frustrating.
Reading this question was a total nightmare = Reading this question was very difficult / hard (to understand).
Teaching Dark Panther Chinese was a total nightmare. = Teaching Dark Panther Chinese was frustrating, difficult, and very annoying. :D :D :D