"Ill-lit" refers to a room or space that has poor lighting, causing it to be dim, gloomy, and often difficult to navigate. Synonyms for this term include poorly-lit, dimly-lit, badly-lit, and shadowy. Other potential synonyms for ill-lit might include dim, murky, gloomy, somber, and darkened. If you're describing a room that's uncomfortable to be in due to its lighting conditions, "dreary," "dull," or "uninviting" could also work as synonyms. When choosing synonyms for "ill-lit," it's important to think about the tone you want to convey, as well as the specific qualities of the lighting in question.