Definition of critical

• marked by a tendency to find and call attention to errors and flaws; "a critical attitude"
• 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"
• characterized by careful evaluation and judgment; "a critical reading"; "a critical dissertation"; "a critical analysis of Melvilles writings"