The Oxford Thesaurus An A-Z Dictionary of Synonyms - fly-by-nightadj.

1) temporary, short-lived, transitory, fugitive, ephemeral, transient, fleeting, passing, brief, impermanent, here today, gone tomorrow: That fly-by-night operation was in business for less than a month. 2) unreliable, untrustworthy, disreputable, irresponsible, dubious, questionable; shifty, dishonest, sharp, crooked, Colloq shady, Brit cowboy: Guarantees on double glazing are worthless if installed by some fly-by-night company.