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

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Example Sentences

See Examples For:

fly-by-night

"This scheme was not a quick fly-by-night operation," Blanche said.

From Barron's ● Aug. 12, 2026

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

State subsidies are paid directly to child-care providers, which could enable fraudsters to set up fly-by-night day care to bilk the government.

From The Wall Street Journal ● Jan. 2, 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

Those jars were something you might expect to find in the basement of a fly-by-night medical school, not a house full of children.

From "Miss Peregrine's Home for Peculiar Children" by Ransom Riggs

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