Investigational refers to something that is being studied or researched, but has not yet been fully proven or established. It can be used to describe a new treatment, drug, therapy, or device that is still in the experimental stage and has not yet been approved for widespread use. The term often appears in clinical trials, where an investigational treatment may be tested on human subjects to determine its safety and effectiveness. In such cases, it means that the treatment is not considered standard of care or a proven option, but rather something that is being explored as a potential solution.