The word zappiest is an adjective that refers to something lively, energetic, and vibrant. The antonyms for this word could include dull, gloomy, lifeless, listless, and sluggish. These words describe something that is lacking in energy, excitement, or enthusiasm. For instance, a boring lecture can be described as dull as it fails to capture the audience's attention. A dark and gloomy day can be called lifeless as it lacks the vibrancy of sunshine. Listless refers to something that lacks energy or enthusiasm, such as a person who is feeling unwell. Lastly, sluggish describes something that is slow-moving and unresponsive.