A sack coat is a type of jacket that has a straight, loose-fitting design with minimal shaping at the waist. It is typically worn as a casual or semi-formal jacket. This type of coat can also be known as a "sack jacket," "sack blazer," or "sack suit." Other synonyms for this type of jacket include "sports coat," "blazer," "sport jacket," or "odd jacket." These terms are often used interchangeably and can refer to different variations of the classic sack coat design. They are all versatile pieces that can be dressed up or down depending on the occasion and personal style.