If "lucid" means clear and easy to understand:
* Obscure: This means unclear, difficult to understand, or hidden.
* Vague: This means not clearly expressed or defined.
* Confused: This means unclear in thought or understanding.
* Muddy: This is a more informal word that means unclear and confusing.
* Unintelligible: This means impossible to understand.
If "lucid" means mentally alert and aware:
* Confused: This means disoriented and unable to think clearly.
* Delirious: This means experiencing a state of wild excitement and irrational behavior.
* Comatose: This means in a deep state of unconsciousness.
* Unconscious: This means lacking awareness or responsiveness.
If "lucid" means bright and shining:
* Dim: This means lacking brightness.
* Dull: This means lacking luster or brilliance.
* Gloomy: This means dark and depressing.
* Opaque: This means not allowing light to pass through.
The best antonym for "lucid" will depend on the specific context and the meaning you wish to convey.