Designating or of an enterprise or undertaking that is illegal, unethical, irregular, unauthorized, etc.; specif., designating a labor strike in violation of a contract and not officially authorized by the union representing the strikers.
Webster's New World
Operating or accomplished outside the norms of standard, ethical business procedures.
Wildcat life insurance schemes.
Of, relating to, or being an oil or natural-gas well drilled speculatively in an area not known to be productive.