cowboy
n. countablen. a person who does a job in a dishonest or careless way. You use this to describe someone who works without the right skills or ignores safety rules to save money.
n. a person who operates a business or performs a trade in an unscrupulous, reckless, or unprofessional manner. Informal in register; frequently used in British English to describe unqualified tradespeople.
The cowboy builder left the roof leaking after taking our money.
The city is cracking down on cowboy operators who ignore safety regulations to undercut legitimate businesses.
Homeowners are often lured by low quotes from cowboy contractors, only to find that the structural work fails to meet even the most basic building codes.
PIE word *gʷṓws From cow + boy. More on Wikipedia.
Often used as a modifier before another noun, such as 'cowboy builder' or 'cowboy outfit'.