Commonsensical is a word that describes something that is grounded in practicality and based on sound judgment. Antonyms for commonsensical could be words such as illogical, absurd, nonsensical, irrational or impractical. These words describe things that lack good sense or reasoning, and the opposite of what is considered to be commonsensical. For example, an illogical decision may be made based on emotions rather than facts. Something that is nonsensical may be considered foolish or ridiculous. Similarly, an irrational or impractical decision may lead to unwanted consequences. It is important to consider all options and make commonsensical decisions that are grounded in reason and logic, rather than impulsivity or emotions.