Crisis

A crisis (from the Greek κρίσις - krisis; plural: "crises"; adjectival form: "critical") is any event that is going (or is expected) to lead to an unstable and dangerous situation affecting an individual, group, community, or whole society. Crises are deemed to be negative changes in the security, economic, political, societal, or environmental affairs, especially when they occur abruptly, with little or no warning. More loosely, it is a term meaning "a testing time" or an "emergency event".
Crises

A crisis (from the Greek κρίσις - krisis; plural: "crises"; adjectival form: "critical") is any event that is going (or is expected) to lead to an unstable and dangerous situation affecting an individual, group, community, or whole society. Crises are deemed to be negative changes in the security, economic, political, societal, or environmental affairs, especially when they occur abruptly, with little or no warning. More loosely, it is a term meaning "a testing time" or an "emergency event".

Wikipedia

Crisis (noun)
A crucial or decisive point or situation; a turning point.
Crisis (noun)
An unstable situation, in political, social, economic or military affairs, especially one involving an impending abrupt change.
Crisis (noun)
A sudden change in the course of a disease, usually at which point the patient is expected to either recover or die.
Crisis (noun)
A traumatic or stressful change in a person's life.
Crisis (noun)
A point in a drama at which a conflict reaches a peak before being resolved.

Wiktionary

Crisis (noun)
a time of intense difficulty or danger
"the monarchy was in crisis"
"the current economic crisis"
Crisis (noun)
a time when a difficult or important decision must be made
"the situation has reached crisis point"
Crisis (noun)
the turning point of a disease when an important change takes place, indicating either recovery or death.

Oxford Dictionary

Crisis (noun)
The point of time when it is to be decided whether any affair or course of action must go on, or be modified or terminate; the decisive moment; the turning point.
Crisis (noun)
That change in a disease which indicates whether the result is to be recovery or death; sometimes, also, a striking change of symptoms attended by an outward manifestation, as by an eruption or sweat.

Webster Dictionary

Crisis (noun)
an unstable situation of extreme danger or difficulty;
"they went bankrupt during the economic crisis"
Crisis (noun)
a crucial stage or turning point in the course of something;
"after the crisis the patient either dies or gets better"

Princeton's WordNet