The word "kafiri" is an Arabic term that is used to refer to an unbeliever or a non-believer in Islam. However, the word is considered derogatory by many and is often used as an insult. Therefore, it's important to use some of the available synonyms to avoid causing offense or using inappropriate language. Some of the commonly used synonyms for "kafiri" include infidel, heathen, pagan, non-believer, unbeliever, and atheistic. These words can be used in contexts where the word "kafiri" might be considered inappropriate or insensitive, and using them instead helps to promote tolerance and respect towards people of different beliefs and cultures.