What is the best definition for the word "incessant"?

The word "incessant" is best defined as "constant." It describes something that continues without interruption or pause. When something is incessant, it typically emphasizes a persistent quality, often implying that it is relentless and ongoing, such as incessant noise or incessant rain. This definition conveys the idea of continuity and a lack of breaks, making it accurate in capturing the essence of the term.

Other definitions do not align well with the meaning of "incessant." For example, "complicated" relates to something being intricate or not easy to understand, "uncertain" refers to doubt or lack of clarity, and "frightening" pertains to inducing fear. None of these capture the key concept of continuity that "incessant" conveys. Thus, the choice defining it as "constant" aligns perfectly with the word's meaning.