"Un chaster" is a French term that translates to "unchaste" in English. This word is typically used to describe someone who is immoral or promiscuous. If you want to find synonyms for "un chaster," there are several words that might fit the bill. These include "immoral," "promiscuous," "unchaste," "loose," "debauched," "dissolute," "licentious," "lewd," "salacious," "indecent," and "immodest." Depending on the context in which you are using the word, any of these synonyms might be a suitable replacement for "un chaster." It's important to choose the right synonym so that you can communicate your message clearly and accurately.