Antonyms of adj efficacious

2 senses of efficacious

Sense 1
efficacious (vs. inefficacious) -- (marked by qualities giving the power to produce an intended effect; "written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley; "the medicine is efficacious in stopping a cough")

inefficacious (vs. efficacious) -- (lacking the power to produce a desired effect; "laws that are inefficacious in stopping crime")

Sense 2
effective (vs. ineffective), effectual, efficacious -- (producing or capable of producing an intended result or having a striking effect; "an air-cooled motor was more effective than a witch's broomstick for rapid long-distance transportation"-LewisMumford; "effective teaching methods"; "effective steps toward peace"; "made an effective entrance"; "his complaint proved to be effectual in bringing action"; "an efficacious law")


Similarity of adj efficacious

2 senses of efficacious

Sense 1
efficacious (vs. inefficacious) -- (marked by qualities giving the power to produce an intended effect; "written propaganda is less efficacious than the habits and prejudices...of the readers"-Aldous Huxley; "the medicine is efficacious in stopping a cough")
       => effective -- (works well as a means or remedy; "an effective reprimand"; "a lotion that is effective in cases of prickly heat")
          Also See-> effective#1, effectual#1, efficacious#2

Sense 2
effective (vs. ineffective), effectual, efficacious -- (producing or capable of producing an intended result or having a striking effect; "an air-cooled motor was more effective than a witch's broomstick for rapid long-distance transportation"-LewisMumford; "effective teaching methods"; "effective steps toward peace"; "made an effective entrance"; "his complaint proved to be effectual in bringing action"; "an efficacious law")
       => hard-hitting, trenchant -- (characterized by or full of force and vigor; "a hard-hitting expose"; "a trenchant argument")
       => impelling -- (markedly effective as if by emotional pressure; "impelling skill as a teller of tales"; "an impelling personality")
       => impressive, telling -- (producing a strong effect; "gave an impressive performance as Othello"; "a telling gesture")
       => rough-and-ready -- (crude but effective for the purpose at hand)
          Also See-> efficacious#1; efficient#1; potent#3, strong#4, stiff#4; powerful#1; useful#1, utile#1