Rapidness is a term that refers to the speed or swiftness of an action. To express the opposite meaning of rapidness, several antonyms come to mind, such as slowness, sluggishness, tardiness, and lethargy. Slowness suggests a lack of speed or quickness in completing a task, while sluggishness implies being slow to move or react. Tardiness refers to being late or delayed, while lethargy refers to a lack of energy or enthusiasm. These antonyms are useful in describing the opposite of rapidness, which can be helpful in contexts where slow-paced action is a desirable quality.