Brisknesses is a noun that refers to the quality of being active and energetic. Some antonyms for brisknesses that one could use in place of this word include lethargy, sluggishness, listlessness, apathy, and languor. Lethargy refers to a lack of energy or enthusiasm, while sluggishness suggests a slow-moving, lazy attitude. Listlessness denotes a lack of interest or enthusiasm, while apathy suggests a complete disinterest in the matters at hand. Finally, languor implies a state of calmness or relaxation that is the opposite of brisknesses. By using these antonyms for brisknesses, one can emphasize a lack of activity, energy, or enthusiasm, depending on the connotation that is desired.