Noun
(colloquial) Something important; (with 'the') the most important one, (especially sports) the big game, the big play.
(US, colloquial) One hundred or one thousand dollars.
(US, colloquial) A dollar.
(seismology, colloquial, usually with the) A hypothetical massive earthquake somewhere along the Pacific coast of North America, but especially one projected to cause catastrophic damage to a major city such as Vancouver, Seattle, San Francisco, or Los Angeles.
(colloquial, by extension) Any other hypothetical event with the potential to be far more devastating than previous events of the same type.
Source: en.wiktionary.orgLike many parts of the West Coast, people in Tofino are on alert for the "Big One" — the magnitude 9.0 earthquake that is expected to hit the B.C. coast someday. Source: Internet
Surveys and studies show that people often are demotivated by efforts to prepare for the Big One, overwhelmed by fatalism in the face of such an event. Source: Internet
In that case, the current pandemic might just have been a “dry run” for the Big One. Source: Internet
It’s the era of the multicar crash, the Big One, when NASCAR’s close-quarters racing can result in chain-reaction melees. Source: Internet