"Plug-ugly" is a derogatory term used to describe someone who is unattractive or unpleasant in appearance, behavior or personality. There are many synonyms for this term, including "ugly," "repugnant," "vile," "repulsive," "disgusting," and "unsightly." Other similar words can be "hideous," "grotesque," "revolting," "foul," "offensive," "abhorrent," "obnoxious," "repellant," "noxious," "gruesome," "unappealing," and "disfigured." Despite their negative connotations, these words can be used to describe a range of physical and personal traits that are unattractive or displeasing. It's important to choose words carefully when discussing someone's appearance or personality to avoid causing needless offense.