Un premeditated means not planned or thought beforehand. There are several antonyms that are opposite to unpremeditated including premeditated, deliberate, intentional, calculated, and purposeful. Premeditated describes something that is planned in advance. Deliberate means something that is done intentionally and consciously. Intentional refers to something that is done with a purpose. Calculated means an action is based on a careful thought process. Purposeful refers to something done with intent to achieve a specific outcome. The antonyms to unpremeditated emphasize the intentionality of an action or thought, highlighting that they are planned and thought through beforehand.