Trying to find opposite word for efficacious in English? No problem. Our site contains antonyms of efficacious in 8 different contexts. We have listed all the opposite words for efficacious alphabetically.
PastTenses is a database of English verbs. One can check verbs forms in different tenses. Use our search box to check present tense, present participle tense, past tense and past participle tense of desired verb.