Critical  adj. 1 a fault-finding, censorious. B expressing or involving criticism. 2 skilful at or engaged in criticism. 3 providing textual criticism (critical edition of milton). 4 a of or at a crisis; dangerous, risky (in a critical condition). B decisive, crucial (at the critical moment). 5 a math. & physics marking a transition from one state etc. To another (critical angle). B (of a nuclear reactor) maintaining a self-sustaining chain reaction.  critically adv. Criticalness n.