adjective Informal.

moving or working at top speed or with maximum effort; all-out: a flat-out effort by all contestants.
downright; thoroughgoing: Many of the paintings were flat-out forgeries.

Origin of flat-out

First recorded in 1925–30
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Related Words for flat-out

all-out, lickety-split

Examples from the Web for flat-out

Contemporary Examples of flat-out

Historical Examples of flat-out

  • This caused some concern over his meager fuel supply since his plan called for some flat-out jetting later on.

    Far from Home

    J.A. Taylor

  • He believed in the New Work, believed in it with every fiber of his being, but an undiverse portfolio was flat-out irresponsible.


    Cory Doctorow