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

Kasdin said, up to now, efforts to negotiate with the residents on Fifth Street have been unsuccessful.

— Miami Herald, Miami Herald, 25 Sep. 2026
Coulter, Hatten, Jones and McMichales all brought unsuccessful challenges against Wilson during last April’s municipal election.

— Olivia Stevens, Chicago Tribune, 25 Sep. 2026

Definition of unsuccessful

Adjective

Before the court fight was launched, Edwin Benn, the arbitrator who oversaw 2023 contract negotiations between the city and FOP, warned the City Council that any attempt to undermine his award to the union would be futile.

— Sam Charles, Chicago Tribune, 24 Sep. 2026
It’s also brilliantly written as a futile, pathetic rebellion by men with zero agency or purpose in their own lives.

— Jim Hemphill, IndieWire, 17 Sep. 2026

Definition of futile

Adjective

Address Employee Resistance And Loss Of Critical Thinking Staff might see AI as a threat to their jobs, which can lead to inefficient use of AI tools.

— Eleonora Liapina, Forbes.com, 25 Sep. 2026
Every year, by design, the law forces thousands of inefficient old vehicles off the road as the cost of compliance rises and parts become harder to find.

— Kyle Cheromcha, The Drive, 24 Sep. 2026

Definition of inefficient

Adjective

Pike’s unsuccessful appeals have alleged ineffective assistance of counsel and argued that executing her would be unconstitutional because of her mental illness, according to court documents.

— Christina Coulter, PEOPLE, 25 Sep. 2026
After powerful antibiotics proved mostly ineffective, the experts from the aquarium and University of Florida developed a bacteriophage treatment for Jetta, according to a statement sent to Popular Science.

— Margherita Bassi, Popular Science, 24 Sep. 2026

Definition of ineffective

Adjective

Future work could seek to understand other results, like finding out exactly when this type of interference from above becomes counterproductive, or what the long-term effects of managers taking more of a hands-on role with sales might be.

— Daniel E. Chavez, The Conversation, 22 Sep. 2026
Those who do play with a single-hander, like Tsitsipas, Italy’s Lorenzo Musetti or Austria’s Lilli Tagger inspire a kind of fascination as to why anyone would go down a path that has become so unusual and supposedly counterproductive.

— Charlie Eccleshare, New York Times, 11 Sep. 2026