in·​ef·​fi·​ca·​cious | \ (ˌ)i-ˌne-fə-ˈkā-shəs How to pronounce inefficacious (audio) \

Definition of inefficacious

: lacking the power to produce a desired effect : ineffective

Keep scrolling for more

Other Words from inefficacious

inefficaciously adverb
inefficaciousness noun

Examples of inefficacious in a Sentence

his efforts to restore the neglected houseplant back to health were belated and sadly inefficacious an inefficacious medication for a rare form of tuberculosis
Recent Examples on the Web 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

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'inefficacious.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of inefficacious

1658, in the meaning defined above

Keep scrolling for more

Learn More about inefficacious

Time Traveler for inefficacious

Time Traveler

The first known use of inefficacious was in 1658

See more words from the same year

Statistics for inefficacious

Cite this Entry

“Inefficacious.” Dictionary, Merriam-Webster, Accessed 14 Jun. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

More from Merriam-Webster on inefficacious

Thesaurus: All synonyms and antonyms for inefficacious


Test Your Vocabulary

Name that Thing: Dog Breeds

True or False

Test your knowledge - and maybe learn something along the way.


Anagram puzzles meet word search.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!