From Longman Dictionary of Contemporary Englishfirst offfirst offinformal a) before doing anything else First off I’d like you all to fill in an evaluation sheet. b) used before saying the first of several things you want to say, especially when you are annoyed First off I didn’t agree with the comments in your email. → first
Examples from the Corpus
first off• Well, first off, I want to know what you've done with the money I gave you. 