Which word describes something that is highly involved or intricate?

The correct choice, "Byzantine," aptly describes something that is highly involved or intricate. The term originates from the complex and convoluted nature of the governance and architecture of the Byzantine Empire, which was known for its elaborate structures and intricate political systems. Therefore, when something is termed as Byzantine, it suggests a level of intricacy and difficulty that requires significant effort to understand or navigate, moving beyond mere complication into a realm of sophistication and complexity.

The other options do not convey this sense of intricacy. "Simplistic" suggests an oversimplified view, lacking depth or detail. "Elementary" refers to something that is basic or foundational, which is the opposite of intricate. "Clear-cut" indicates something that is straightforward and unambiguous, further emphasizing a lack of complexity. Thus, "Byzantine" is the only choice that accurately captures the essence of being highly involved or intricate.