The word "vermicious" may not be a commonly used word in today's language, but there are several synonyms for it. Some of the possible words that carry similar meanings include toxic, harmful, deadly, foul, venomous, putrid, and noxious. Each of these words suggests a sense of danger, warning the listener or reader to beware of what might come, to avoid harm and danger, or to protect oneself from poisonous and deadly substances. The use of such synonyms brings out the depth of meaning and intensity that goes with the word "vermicious." These words are best used when describing dangerous situations, toxic substances, or harmful living conditions.