Learner's definition of DISASTER
1 [count] : something (such as a flood, tornado, fire, plane crash, etc.) that happens suddenly and causes much suffering or loss to many people
The program examined several bridge failures and other engineering disasters.
a nuclear disaster
The earthquake was one of the worst natural disasters [=a disaster caused by natural forces] of this century.
The state is asking for federal disaster relief. [=money to help rebuild an area after a disaster]
2 a : something that has a very bad effect or result
b [count] : a complete or terrible failure
They're trying to find a way to avoid disaster.
They narrowly escaped disaster.
The new regulations could spell disaster [=result in serious problems] for smaller businesses.
The government's policy is a recipe for disaster. = The government is flirting with disaster by pursuing this policy.
When disaster strikes, [=when something very bad happens] we will be prepared.