Lightlessness refers to the state of being without light or darkness. This concept can be described in various ways using synonyms. One such synonym is "obscurity," which suggests a lack of clarity or brightness. Another synonym for lightlessness is "blackout," which refers to a temporary loss of power or light, often due to a natural disaster or man-made event such as a power cut. "Gloom" is another synonym that denotes a state of partial darkness or low light. "Dimness" suggests a lack of brightness or clarity and could be used to describe environments that are poorly lit. Overall, there are several synonyms that can be used to describe the state of lightlessness.