A crucial or decisive point or situation; a turning point.

An unstable situation, in political, social, economic or military affairs, especially one involving an impending abrupt change.

(medicine) A sudden change in the course of a disease, usually at which point the patient is expected to either recover or die.

(psychology) A traumatic or stressful change in a person's life.

(drama) A point in a drama at which a conflict reaches a peak before being resolved.