Which word refers to someone completely unaware of their surroundings?

The term "oblivious" specifically describes a state of being completely unaware of what is happening around oneself. It captures the essence of having no conscious recognition or understanding of the environment or situations. Someone who is oblivious is not only unaware but may also appear indifferent or detached from their surroundings, making this term particularly fitting for the question.

In contrast, "aware," "perceptive," and "mindful" all imply a level of awareness or consideration regarding one's environment or feelings. These words suggest an ability to notice, understand, or engage with what is occurring, which aligns with being cognizant rather than unaware. Thus, they do not accurately represent someone lacking awareness. This distinction highlights why "oblivious" is the appropriate choice in this context.