Any of the freebooters preying on Spanish ships and settlements especially in 17th century West Indies. (Merriam – Webster)
An unscrupulous adventurer especially in politics or business. (Merriam – Webster)
A buccaneer was a pirate. Buccaneers often attacked and stole from Spanish ships in the 17th and 18th centuries. (Collins Dictionary)
If you describe someone as a buccaneer, you mean that they are clever and successful, especially in business, but you do not completely trust them. (Collins Dictionary)
A person who attacked and stole from ships at sea, especially someone allowed by a government to do this in the 17th and 18th centuries. (Cambridge Dictionary)
A pirate, originally one operating in the Caribbean. (Oxford Dictionaries)
A person who acts in a recklessly adventurous and often unscrupulous way, especially in business. (Oxford Dictionary)
Examples
Buccaneer, Wikipedia.

https://en.wikipedia.org/wiki/Buccaneer
What is the difference between a pirate and a Buccaneer.

http://mentalfloss.com/article/85933/whats-difference-between-pirate-and-buccaneer