unfailing

adjective

un·​fail·​ing ˌən-ˈfā-liŋ 

: not failing or liable to fail:

a

: constant, unflagging

unfailing courtesy

b

: everlasting, inexhaustible

a subject of unfailing interest

c

: infallible, sure

an unfailing test

unfailingly

ˌən-ˈfā-liŋ-lē 

adverb

Synonyms

• unerring
• reliable
• perfect
• flawless
• infallible

Examples of unfailing in a Sentence

She is known for her unfailing optimism.

an unfailing judge of personal character

Recent Examples on the Web

Developed at the height of the Cold War, GPS was designed by the Pentagon to give US forces an unfailing sense of position anywhere on Earth. —Kapil Kajal, Interesting Engineering, 11 Sep. 2025

In a world where trust now comes at a premium, trust in your GenAI strategy starts with trusting the data that fuels it, and the most unfailing data in your business lives in your contracts. —Monish Darda, Forbes.com, 8 Sep. 2025

Yesterday’s pangrams were gainful, unfailing and unflagging. —Julia Jacobs, New York Times, 19 May 2025

What is most important, always, is an unfailing loyalty to Trump. —Constance Grady, Vox, 25 Apr. 2025

Word History

First Known Use

14th century, in the meaning defined above

Rhymes for unfailing

• assailing
• availing
• bewailing
• blackmailing
• curtailing
• derailing
• descaling
• detailing
• dovetailing
• entailing
• exhaling
• impaling

Kids Definition

unfailing

adjective

un·​fail·​ing ˌən-ˈfā-liŋ 

ˈən-

1

: not likely to fail : constant, unflagging

unfailing support

2

: not likely to run out or be used up : everlasting, inexhaustible

an unfailing supply

3

: infallible sense 2

the unfailing mark of an amateur

unfailingly adverb