flat out
1 as fast or as hard as possible.
2 without hesitation or reservation; unequivocally. chiefly North American
❶ 2013Daily Telegraph In April this year another commissioner, Stephen Betts, who oversees the Norfolk force, was forced to apologise after saying skilled drivers should be allowed to drive 'flat out' on the motorway.
❷2013Bryan Caplan, Arnold Kling & David HendersonLibrary of Economics & Liberty-Econlog That's just a flat false and ugly accusation, based on a fundamental misunderstanding of the concept of the government's responsibility. It is actually quite appalling Yglesias would insinuate or flat out state otherwise.