costly

adjective

cost·​ly ˈkȯs(t)-lē 

costlier; costliest

1

a

: commanding a high price especially because of intrinsic worth

costly gems

b

: rich, splendid

2

: made or done at heavy expense or sacrifice

a costly mistake

costliness noun

Synonyms of costly

• expensive
• valuable

Examples of costly in a Sentence

We use less costly materials in our products.

It was too costly to fix her car after the accident, so she decided to buy a new car instead.

They won the game, but their best player was injured, so it was a costly victory.

The decision to wait could be a costly mistake.

Recent Examples on the Web

But many more have trouble affording the costly shots. —CBS News, 23 Dec. 2025

Rookie safety Lathan Ransom hauled in an interception with less than a minute left in the game — sealing the 23-20 win and redeeming himself after a costly, last-minute penalty against the Saints a week ago. —Alex Zietlow, Charlotte Observer, 22 Dec. 2025

Once hotly debated as an experimental, costly pitch to restore the vulnerable eastern span in the wake of the 1989 Loma Prieta earthquake, the rebuilt Bay Bridge now has more than a decade under its belt serving one of the Bay Area’s most vital transportation arteries. —Katie Lauer, Mercury News, 22 Dec. 2025

Continually curating fresh data and retraining detectors is costly, and detectors inevitably lag behind the systems they are meant to identify. —Ambuj Tewari, Fortune, 22 Dec. 2025

Word History

First Known Use

14th century, in the meaning defined at sense 1a

Kids Definition

costly

adjective

cost·​ly ˈkȯs(t)-lē 

costlier; costliest

1

: of great cost or value

costly furs

2

: gained at great expense or sacrifice

a costly victory

costliness noun