What term describes weather conditions that result in excellent visibility for pilots?

The term that describes weather conditions resulting in excellent visibility for pilots is "CAVU," which stands for "Ceiling And Visibility Unlimited." This term indicates that both the cloud ceiling and the visibility are at optimal levels, allowing for clear and unobstructed flying conditions. In aviation, CAVU is highly desirable because it ensures that pilots can navigate safely and effectively without encountering reduced visibility due to weather phenomena such as fog, rain, or snow.

In contrast, the other options describe different concepts or conditions. For example, VATB refers to visibility reports but does not specifically denote excellent conditions as CAVU does. AXIS typically pertains to a line of reference or rotation in various contexts, and CALM refers to a lack of wind conditions rather than visibility itself. Thus, CAVU is the most accurate term identifying excellent visibility in the context of aviation.