fly-by-night

noun

1. 1

   A creature which flies at night; a nocturnal flier or traveler.

2. 2

   One who departs or flees at night in order to avoid creditors, law enforcement etc.

   “Do not give your credit card number to that fly-by-night operation.”

3. 3

   A person or business that appears and/or disappears rapidly, appearing untrustworthy, or giving an impression of transience.

4. 4

   A traveling businessman or tradesman.