Definition of bracket-buster in English:

bracket-buster

noun

US
  • 1(in the NCAA college basketball tournament) a low-ranking team that unexpectedly defeats a high-ranking team.

    ‘their impressive win total has led many to tout them as a potential bracket-buster’
    1. 1.1 A game in which a low-ranking team unexpectedly defeats a high-ranking team.
      ‘in yet another bracket-buster, the March Madness upsets continued’

Origin

1990s: from bracket (sense 5 of the noun) + buster (sense 2).