( informal ) used to emphasize that you are telling the truth or will do what you promise :
I saw him do it—cross my heart.
( informal ) used to emphasize that you are telling the truth or will do what you promise :
I saw him do it—cross my heart.
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005