fly-by-night 1 adj. Set up to make a lot of money in a hurry, then disappear so people can't find you to complain about poor work, etc.; not trustworthy; not reliable. Mrs. Blank bought her vacuum cleaner from a new company; when she tried to have it fixed, she found it was a fly-by-night business.
fly-by-night 2 n. , informal 1. A company that sells many cheap things for a big profit and then disappears. A dependable company honors its guarantees, but a fly-by-night only wants your money. 2. A person who does not pay his bills, but sneaks away (as at night.) Hotels are bothered by fly-by-nights.