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Fly by night 

Type of contractor that takes %50 deposit from home owners in new communities then disappears over night with multiple hundreds of the unsuspecting victims loot.

To get high in the evening.

To start a bender this Friday that steamrolls Monday meetings.

A magic carpet ride when you rent a limo bus for an out of town party tour for the summer and go on tour singing live operatuneist.
Some of them irrigation contractors are fly by night so be sure to ask for their certification # from Centre For Irrigation Technology.

fly by night 

A slang term used to describe someone or more than one person (can be as large as a business or any other entity) who is extremely unreliable, unless they want something from you. To put these dirtbags in their place, one must confront them directly face to face. This term is different than a flake, as a fly by night DOES contact a person, but only when they want something, whereas a flake or flaky person DOES NOT.
Tim was such a fly by night about turning in that homework for our group, he got us an F! But then when he wanted a ride home from the bar, he contacted us left and right! That guy can walk his ass 3 miles to get home!

Kurt's fly by night attitude caused him to not be liked by his friends, and for him to only get sex from more undesirable types of women with hairy vaginas.
fly by night by johnnyb69 January 31, 2010

fly by night 

means get out of town fast
After I pull this last Bank job I'm gona fly by night... You know isa got the ghz. Isa hertz'n so bad I'm gona fly this old koop by night back to alie-bama get's some good grits.
fly by night by itichie_nocanpo October 17, 2006

fly-by-night 

an unprincipled person who just gets involved with someone or a job to meet their need and evacuates to next donor.
Watch out Kim, he's a fly-by-night, he'll use you and be gone in the morning.
fly-by-night by prodigal's boss December 23, 2014

fly by night mother fucker

The type of person who is shady, scandalous and typically does dirt in the late hours or very early morning. May have a girlfriend but never sees her due to his extracurricular activities he chooses.
Girl you don’t need him, he’s one of those fly by night mother fuckers.
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Origin of the word is unknown. Started sometime in World War 2. Given the typical evolution of British slang, could easily have started because what these experts did was confusing or “baffling” to the common person.
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I saw Satantango last night, wonderful film but by the 5th hour I had to start doing pee calculus.
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