1
general::
An exclamation expressing surprise, alarm, dismay, or some other, usually negative emotion. For example, Good grief! You're not going to start all over again, or Good grief! He's dropped the cake. The term is a euphemism for "good God." [Early 1900s]
American Heritage Idioms
2
general::
Phrase(s): Good grief!
Inf. an exclamation of surprise, shock, or amazement. • Alice: Good grief! I’m late! Mary: That clock’s fast. You’re probably okay on time. • Bill: There are seven newborn kittens under the sofa! Jane: Good grief!
McGrawhill's American Idioms And Phrasal Verbs