The word "priestish" refers to something related to or resembling a priest, which includes their mannerisms, behavior, or dress. Some synonym for "priestish" could be "clerical," which can refer to the clergy of a particular religion, or "ecclesiastical," which pertains to the church or its functions. "Papal" could also be a synonym for "priestish," as it refers to the pope or the papacy. Another word that is similar in meaning to "priestish" is "reverential," which means showing deep respect or awe for something. "Devout" is another word that could be used as a synonym, which means deeply religious or spiritual.