Longman Dictionary of Contemporary English
three-piece suit
noun
EXAMPLES FROM CORPUS
▪ At this point, a large man in a brown three-piece suit ahead of me looked up from a sheaf of notes.
▪ Hank would arrive each morning, dressed in his neat three-piece suit, white shirt, and solid-color tie.
▪ He wore an immaculately tailored three-piece suit, cut from a cloth of apricot cream.
▪ Her immigrant father with his thick mustache and accent and three-piece suit would only bring her more ridicule.
▪ In spite of the heat he was very smartly dressed in a dark three-piece suit.
▪ Suddenly like Matisse in a three-piece suit and consultant's white coat, I take infinite pains to keep this model alive.
▪ The Prime Minister carried a fly whisk and a cane and wore a three-piece suit.
Wiktionary
three-piece suit
n. A suit consisting of matching jacket, trousers(,) and waistcoat.
WordNet
three-piece suit
n. a business suit consisting of a jacket and vest and trousers
Usage examples of "three-piece suit".
Success is hard enough to achieve without showing up on casual Friday in a three-piece suit.
He was wearing a black three-piece suit, and I knew right away that he was not a human being, because his eyes were the orangey red of flames in a woodstove.
Remo opened the back door on a lemon-faced man in a gray three-piece suit and striped Dartmouth tie.