Hackdriver is a term commonly used in British English to describe a taxi driver who operates without a license or any regulatory oversight. There are many synonyms for this term, including "black-cab driver," "unlicensed taxi driver," "gypsy cab driver," and "pirate taxi driver." These terms all refer to individuals who provide transportation services without meeting the legal requirements to do so. While the use of unlicensed drivers may seem like a harmless option for travelers looking to save money, these operators often lack appropriate insurance coverage and may not have undergone background checks to ensure passenger safety. As such, it is always advisable to stick to licensed taxi or rideshare services.