Which word describes an individual who lacks energy and enthusiasm?

The word "listless" effectively describes someone who lacks energy and enthusiasm. When a person is listless, they exhibit a sense of lethargy or disinterest, often appearing inactive or apathetic. This term conveys a state of being without motivation or vigor, which aligns precisely with the idea of lacking energy and enthusiasm.

In contrast, "vibrant," "effusive," and "dynamic" all connotate high energy and enthusiasm. A vibrant individual is full of life and vitality, an effusive person expresses feelings in an unrestrained or heartfelt manner, and a dynamic person displays persistent change or activity. Thus, these alternatives do not fit the definition of lacking energy or enthusiasm as "listless" does.