Definition of a tall tale in English:

a tall tale

phrase

(also a tall story)
  • An account that is fanciful and difficult to believe.

    ‘speakers delighted the audience with true stories and tall tales’
    • ‘he would regale me with some of his tall stories’
    unlikely, improbable, exaggerated, far-fetched, implausible, dubious, overblown, unbelievable, incredible, preposterous, outrageous, absurd