flat-out

/F L AE1 T AW1 T/
adjective
  1. 1

    Complete, total, downright.

  2. 2

    Very busy.

  3. 3

    Lazy, sleeping.

    โ€œflat out (like a lizard in the sun) - doing absolutely nothingโ€

adverb
  1. 1

    At top speed.

    โ€œAfter 10 minutes of running flat out, he was out of breath.โ€

  2. 2

    Bluntly, no holds barred, totally, outright.

    โ€œHe was flat out furious when his car was stolen.โ€

Source: https://en.wiktionary.org/wiki/flat%20out, https://en.wiktionary.org/wiki/flat-out