The word "un-thinking" is an adjective that is often used to describe someone who is not using their brain or who is not considering the possible consequences of their actions. If we are looking for antonyms for this word, we will find several options that can help us to express the opposite meaning. Some of these antonyms include thoughtful, considerate, mindful, intelligent, wise, reflective, and perceptive, among others. These words indicate that the person is using their brain, analyzing their decisions, and taking into account the impact on themselves and others. Using these antonyms can help us to emphasize the importance of being conscious and responsible in our actions and decisions.