Blue  —adj. (bluer, bluest) 1 having the colour of a clear sky. 2 sad, depressed. 3 pornographic (a blue film). 4 politically conservative. —n. 1 blue colour or pigment. 2 blue clothes or material (dressed in blue). 3 person who represents a university in a sport, esp. Oxford or cambridge. 4 conservative party supporter. —v. (blues, blued, bluing or blueing) 1 make blue. 2 slang squander.  once in a blue moon very rarely. Out of the blue unexpectedly. [french from germanic]