Pier glasses are a type of large mirror that was often placed between windows on a wall, specifically on a pier. They were quite popular in the 18th and 19th centuries and are still used in some interiors today. While "pier glass" is the most common term for this type of mirror, there are several synonyms that can be used interchangeably. Some of these include "console mirror," "mantel mirror," "overmantel mirror," and "wall mirror." Each of these terms refers to a mirror that is positioned in a specific place within a room and has a particular purpose or function.