Insomnious is a rarely used word that describes a person who cannot sleep or suffers from insomnia. Antonyms are words that mean the opposite of a particular word. Therefore, antonyms for insomnious would be words that mean someone who sleeps soundly or has no problem falling asleep. These antonyms could include a variety of words such as restful, peaceful, tranquil, and sleepy. Other synonyms for insomnious could include drowsy, lethargic, or somnolent, which all suggest someone who is very tired and easily falls asleep. Regardless of what antonyms one chooses to use, it is clear that insomnious describes someone who has difficulty sleeping, whereas antonyms describe those who find sleep easy and restful.