fly-by-night
/ˈflaɪbaɪnaɪt; `flaɪ baɪ ˌnaɪt/ n
(pl fly-by-nights) person who evades financial responsibility, esp debts, by (secretly) leaving; unreliable person 为躲债（偷偷）离去的人; 不可靠的人. adj unreliable or dishonest, esp in financial and business matters 不可靠的; 不诚实的（尤指在财务及商业事务上）
a fly-by-night company 无信誉的公司.