Three-piecers is a slang term used to describe a type of suit that consists of a jacket, trouser, and a waistcoat. However, there are other synonyms that can be used to describe this type of suit. One synonym is "three-piece suit," which is similar to the original term. Another term that is frequently used is "vested suit," which is a reference to the waistcoat component of the suit. Other synonyms for three-piecers include "full suit", "formal suit", "buttoned suit", "ensemble", "coat, waistcoat and trousers set" and "matching suit". These terms can be used interchangeably depending on the context and the personal preference of the speaker.