critical in WordNet English dictionary

1. marked by a tendency to find and call attention to errors and flaws
   "a critical attitude"
   critical 
   
2. characterized by careful evaluation and judgment
   "a critical reading"; "a critical dissertation"; "a critical analysis of Melville's writings"
   critical 
   
3. being in or verging on a state of crisis or emergency
   "a critical shortage of food"; "a critical illness"; "an illness at the critical stage"
   critical 
   
4. at or of a point at which a property or phenomenon suffers an abrupt change especially having enough mass to sustain a chain reaction
   "a critical temperature of water is 100 degrees C--its boiling point at standard atmospheric pressure"; "critical mass"; "go critical"
   critical 
   
5. of or involving or characteristic of critics or criticism
   "critical acclaim"
   critical 
   
6. forming or having the nature of a turning point or crisis
   "a critical point in the campaign"; "the critical test"
   critical  decisive 
   
7. urgently needed; absolutely necessary
   "a critical element of the plan"; "critical medical supplies"; "vital for a healthy society"; "of vital interest"
   critical  vital