fly-by-night

[ flahy-bahy-nahyt ]
/ ˈflaɪ baɪˌnaɪt /

adjective

not reliable or responsible, especially in business; untrustworthy: a fly-by-night operation.
not lasting; brief; impermanent; transitory: a fly-by-night theater.

noun Also fly-by-night·er.

a person or thing that is unreliable, especially a debtor who evades or attempts to evade creditors.
a person regarded as a poor credit risk.

Origin of fly-by-night

First recorded in 1790–1800
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for fly-by-night

British Dictionary definitions for fly-by-night

fly-by-night
/ informal /

adjective

unreliable or untrustworthy, esp in finance
brief; impermanent

noun Also: fly-by-nighter

an untrustworthy person, esp one who departs secretly or by night to avoid paying debts
a person who goes out at night to places of entertainment
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Culture definitions for fly-by-night

fly-by-night

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.”

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.