#1 coolness n. [imperturbability, imperturbableness] calm and unruffled self-assurance; "he performed with all the coolness of a veteran". wn #2 coolness n. [chilliness, nip] the property of being moderately cold; "the chilliness of early morning". wn #3 coolness n. [nervelessness] fearless self-possession in the face of danger. wn #4 coolness n. [coldness, frigidity, frigidness, iciness, chilliness] a lack of affection or enthusiasm; "a distressing coldness of tone and manner". wn