critical

Extremely important.

quick to say what is wrong or bad about someone or something

Of a patient condition involving unstable vital signs and a prognosis that predicts the condition could worsen; or, a patient condition that requires urgent treatment in an intensive care or critical care medical facility.

In such a condition.

Relating to criticism or careful analysis, such as literary or film criticism.

Employing or related to textual criticism, particularly through a stemmatological comparison of all extant texts and reconstruction of the original.

Pertaining to, or indicating, a crisis or turning point.

Likely to go out of control if disturbed, that is, opposite of stable.

Of the point (in temperature, reagent concentration etc.) where a nuclear or chemical reaction becomes self-sustaining.

Of a temperature that is equal to the temperature of the critical point of a substance, i.e. the temperature above which the substance cannot be liquefied.

Needing great discrimination to be correctly classified; easily confused.

A critical value, factor, etc.

critical hit

In breakdancing, a kind of airflare move in which the dancer hops from one hand to the other.