Cockamamy is a word that means something ridiculous or absurd. Its antonyms could include sensible, reasonable, logical, practical, realistic, and coherent. These words are in opposition to the frivolous, nonsensical meanings of cockamamy. They imply the presence of sound judgment, solid arguments, and factual information that supports it. Additionally, the use of synonyms to cockamamy, such as preposterous, ludicrous, and absurd, could be considered antonyms as well. The antonyms of cockamamy cater to serious and thoughtful people, whereas the word itself is more appropriate for those who are fond of jokes and humor.