Mother of God

Short definition from Wiktionary

Proper noun

1. 1
   A dogmatic title of Mary, mother of Jesus, in particular reference to her role as mother of God (God the Son).

Interjection

1. 1
   Said in supplication to Mary.
2. 2
   An expression of surprise.
3. 3
   An expression of disgust, annoyance, or disappointment.