What condition describes fur that lacks density in the undercoat?

The condition described as fur that lacks density in the undercoat is referred to as a loose coat. A loose coat indicates that the rabbit's undercoat is not as full or dense as it should be, which can affect insulation and overall appearance. This condition can result from various factors, such as genetics, health issues, or suboptimal environmental conditions. Adequate undercoat density is essential for regulating a rabbit's body temperature and protecting it from the elements.

The other terms relate to different aspects of rabbit care and characteristics. Lopped ear refers to a particular ear shape that some breeds have, where the ears hang down instead of standing upright. Malocclusion is a dental condition where the rabbit's teeth do not align correctly, leading to potential health problems. Luster describes the shine or sheen of the fur, which is an indicator of good health and coat maintenance. However, none of these terms directly indicate a lack of density in the undercoat.