1. the financial industry's term for a rainmaker; a Wall Street executive who brings in enormous amounts of money for the firm, possibly because he has just screwed a customer.
An expression made famous by Michael Lewis in Liar’s Poker, published in 1989.
2. a mover and shaker in any organization
Calling some one a dick is an insult.
Calling some one a big dick is a bigger insult.
Calling some one a big swinging dick is a term of respect.