A devastating Earthquake that strikes the San Andreas fault line about every 100 years, last happening hitting in The 1906 San Francisco Earthquake. Most commonly used in reference to a predicted future earthquake.
I think we should invest in some sturdier infrastructure here. I mean, what about when the Big One hits?
It's the one people always talk about, the mythical/legendary big one. why isn't it already defined?
Refers to anything big, a big piece of food, a big sex organ, a big butt, or anything else that is big.