| Efficacious (a.) Effective; productive, or powerful to produce the effect intended; as, an efficacious law. Thesaurus Entries able, active, adequate, authoritative, capable, charismatic, charming, competent, consequential, effective, effectual, efficient, enchanting, equal to, estimable, functional, go, important, influential, magnetic, momentous, operational, operative, personable, persuasive, potent, powerful, practical, prestigious, productive, proficient, puissant, reputable, serviceable, strong, suasive, substantial, successful, telling, up to, useful, virtuous, weighty, winning |