1
general::
Phrase(s): in no uncertain terms
Cliché in very specific and direct language. • I was so mad. I told her in no uncertain terms to leave and never come back. • I told him in no uncertain terms to stop calling me.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Emphatically, definitely so. For example, Jane told them in no uncertain terms that she wanted no part of their practical joke. The double negative in this idiom serves for emphasis. [Mid-1900s] Also see IN SO MANY WORDS.
American Heritage Idioms