mea culpa
Concise Oxford English Dictionary © 2008 Oxford University Press:
mea culpa /ˌmeɪə ˈkʊlpə, ˌmiːə ˈkʌlpə/
▶exclamation used as an acknowledgement of one's fault or error.
– origin L., ‘by my fault’.
'mea culpa' also found in these Oxford entries:

