fly-by-night

American  

[flahy-bahy-nahyt] / ˈflaɪ baɪˌnaɪt /

adjective

1. not reliable or responsible, especially in business; untrustworthy.

   a fly-by-night operation.

2. not lasting; brief; impermanent; transitory.

   a fly-by-night theater.

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noun

1. a person or thing that is unreliable, especially a debtor who evades or attempts to evade creditors.

2. a person regarded as a poor credit risk.

fly-by-night British  

adjective

1. unreliable or untrustworthy, esp in finance

2. brief; impermanent

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noun

1. an untrustworthy person, esp one who departs secretly or by night to avoid paying debts

2. a person who goes out at night to places of entertainment

fly-by-night Cultural  

1. Shady or untrustworthy: “Before buying stock in a newly formed company, the prudent investor will check its owners' credentials to make sure it's not a fly-by-night operation.”

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Etymology

Origin of fly-by-night

First recorded in 1790–1800

Example Sentences

See Examples For:

fly-by-night

At the same time, small fly-by-night schools have been opened by profiteers and people with problematic pasts or no educational experience.

From Salon ● Jul. 27, 2026

The proliferation of fly-by-night flags and registers has fanned concern about possible accidents involving old tankers with sanctioned cargoes, but until the recent seizures Western governments have mostly allowed them to sail unimpeded.

From The Wall Street Journal ● Jan. 11, 2026

Anybody who might have assumed that “Rust” was some fly-by-night exploitation flick should know that its bones are very much that of a moody indie with a heart and a conscience.

From Los Angeles Times ● May 2, 2025

There are just too many fly-by-night operations that either treat your personal data carelessly or, in some cases, just steal it.

From Seattle Times ● Feb. 12, 2024

And, God knows, Will had plenty of experience with fly-by-night ideas.

From "East of Eden" by John Steinbeck