INEFFICACIOUS Synonyms: 72 Similar and Opposite Words

inefficacious

adjective

(ˌ)i-ˌne-fə-ˈkā-shəs

Definition of inefficacious

as in unsuccessful

not producing the desired result his efforts to restore the neglected houseplant back to health were belated and sadly inefficacious

Synonyms & Similar Words

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Antonyms & Near Antonyms

as in futile

producing no results an inefficacious medication for a rare form of tuberculosis

Synonyms & Similar Words

Antonyms & Near Antonyms

Example Sentences

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Recent Examples of inefficacious Day — who grew up watching the spelling bee — came up with the concept of exploring the psyche of a winner with an ultimately inefficacious career in 2015 while at a UCB improv sketch-writing class. — NBC News, 6 Oct. 2020

Recent Examples of Synonyms for inefficacious

Adjective

That ability to learn may ultimately separate successful defenders from unsuccessful ones.

— Emil Sayegh, Forbes.com, 30 Aug. 2026
The five unsuccessful trials shared a condition of the test rig rather than indicating a failure of the recovery logic.

— Rupendra Brahambhatt, Interesting Engineering, 29 Aug. 2026

Definition of unsuccessful

Adjective

In sick bay, M’Benga tries to remove the table and end his life so Chapel can give up on him, an effort that proves futile.

— Keith Phipps, Vulture, 27 Aug. 2026
Its storyline spins the futile, determined chase of Wile to one day capture Roadrunner as something admirable, and applies that underdog mentality to the average person trying to navigate a late capitalist landscape that values profits over people.

— Wilson Chapman, IndieWire, 27 Aug. 2026