JDSN stands for "Jeon-do-sah-nihm" and is a common acronym used among Korean-American Christians to refer to any minister.
JDSN is often an unordained pastor, though the term doesn't specifically means it so. "Jeon-do" means "to spread the message" (IIRC!), "sah" mean "a person", and "nihm" is a suffix of respect (similar to "sama" in Japanese.) So JDSN is technically any person who spreads the message, usually of religious in nature, like a missionary. But unlike the word "missionary," a JDSN also refers to someone in home land, often at a local church.
JDSN is a part of the Konglish language.