Definition of efficacious:
effective (part of speech: adjective)
- study at effective
- "The Duke's Children", Anthony Trollope.
- "Weather and Folk Lore of Peterborough and District", Charles Dack.
For he had known that, whatever Eliot Leithgow's method of forcing him to perform the operations might be, and no matter how efficacious, the coordinated brains simply could not be put in the heads of his four assistants- because the assistants were themselves needed for the operations!- "The Passing of Ku Sui", Anthony Gilmore.