Being plain is a term often used to describe a person, object or thing that lacks any kind of ornamentation or decoration. It is a simple and straightforward term and one that is commonly used in literature to describe a person or character. However, there are several other synonyms for the word "being plain" which can be used to add more depth and interest in a sentence. Some of these synonyms include, unadorned, simple, undecorated, uncomplicated, austere, modest, and unembellished. These synonyms can be used interchangeably with "being plain" to add more texture to the description and make it more appealing.