fly-by-night (flībī-nīt′) Informal
adj.1. Unreliable or unscrupulous, especially with regard to business dealings: "some fly-by-night startup that was halfway to shutting down" (Douglas Edwards).
2. Of an impermanent or insubstantial nature: fly-by-night fashions in clothing.
n. also
fly-by-night·er (-n
īt
ər)
1. An unreliable or unscrupulous person.
2. One, such as a company, that is short-lived and therefore unreliable.