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.
by prodigal's boss December 24, 2014
Get the fly-by-night mug.
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.
by Snow Pea - Digit El Poal S.Sa October 23, 2016
Get the Fly by night mug.
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.
by johnnyb69 February 1, 2010
Get the fly by night mug.
Song written by Rush in their 1975 album Fly By Night. Contrary to their debut album, Fly By Night was the first to express elements of Progressive Rock the band is known for
Person 1: Did you hear Fly By Night in R40?
Person 2: No, it wasn't in R40
by newhavenrailroad January 31, 2017
Get the Fly By Night mug.
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.
by itichie_nocanpo October 17, 2006
Get the fly by night mug.
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.
by MakWood January 14, 2018
Get the fly by night mother fucker mug.
A old primary saying derrived from biblical scripture referring to the cosmic unbalance experienced by both humans and birds in an aura of wetness. The shared self interprentence is lost by the swelling darkness of night, and an uncontrolable urge of wisdom not to fly till dawn arrives.
Two guys come out of a pub:

1st Guy: "Lets burn some rubber in da drag races man while its dark! No coppers!"

2nd Guy:"Wet birds don't fly at night... remember that man..."
by Gdogs McC & Natablanca D January 13, 2006
Get the wet birds don't fly at night mug.