The word "in sensibleness" refers to the quality of being rational, logical, and reasonable. Antonyms for this word include irrationality, illogicality, and unreasonableness. These are all traits that are associated with being impractical, senseless, and nonsensical. Another antonym for "in sensibleness" is madness or insanity, which implies a lack of rationality and a disregard for logic. Opposites also include impetuousness or impulsiveness, which refers to acting without thinking or considering the consequences. Overall, antonyms for "in sensibleness" all imply a lack of practicality, wisdom, and rationale, which can lead to poor decision-making and undesirable outcomes in various aspects of life.