english
1
general::
For certain, as in That check will arrive tomorrow morning without fail. This idiom today is used mainly to strengthen a statement. [Early 1700s]
American Heritage Idioms
2
general::
Phrase(s): without fail for certain; absolutely. • I’ll be there at noon without fail. • The plane leaves on time every day without fail.
McGrawhill's American Idioms And Phrasal Verbs