efficacious

0 antonyms and opposites of efficacious, grouped by meaning.

Adj — Effective; possessing efficacy.

We haven't recorded synonyms for efficacious yet. You can still read its full definition, where it comes from, or words that rhyme with it.

Etymology

From Old French efficacieux (whence -acious), from Latin efficāx (“efficacious”) + -ous, from efficere (“to effect, to accomplish”); see effect.