The word "pensivenesses" is a plural noun that refers to a state of deep and serious thought. Some antonyms for pensivenesses include frivolity, levity, cheerfulness, carelessness, and superficiality. Frivolity suggests a lack of seriousness or importance, while levity implies a lightheartedness or humor that contrasts with pensiveness. Cheerfulness is the opposite of pensiveness as it reflects a state of happiness and well-being. Carelessness suggests a lack of concern or attention to detail, and superficiality refers to a shallowness or lack of depth. These antonyms can provide a useful contrast to the serious and contemplative tone of pensivenesses.