Lucidness refers to the quality of being clear and easily understood. Antonyms for this word could include obscurity, vagueness, confusion or perplexity. These terms point to situations where the meaning is not clear or obvious, and may require further interpretation to comprehend fully. Other possible antonyms could include unintelligibility, ambiguity or murkiness, which suggest that the content is muddled and difficult to interpret. Therefore, if someone is struggling to understand a particular concept or idea, it may be described as lacking lucidness, and instead, possess traits of obscurity, confusion, or some other antonym associated with the term.