- The definition of efficacious is someone or something that successfully produced a result that was desired.
An example of efficacious is a program that was designed to help stop crime and that reduced the crime rate by 80 percent.
efficacious definition by Webster's New World
Origin: Classical Latin efficax (gen. efficacis) ; from efficere, to bring to pass, accomplish (see effect) plush -ous
efficacious definition by American Heritage Dictionary
Origin: From Latin efficāx, efficāc-, from efficere, to effect; see effect.
- efˌfi·caˈcious·ly adverb
- efˌfi·caˈcious·ness noun