Technically a chaplain is a clergyman in charge of a chapel. In the USA especially the term is used of a clergyman attached to a branch of the military services. It is used in a military context in Catch 22, by Joseph Heller, where Corporal Whitcomb...

A representative of a church or churches attached to an educational institution to serve the religious needs of staff and...

A chaplain is typically a priest, pastor, ordained deacon or other member of the clergy serving a group of people who are not organized as a mission or church, or who are unable to attend church for various reasons; such as health, confinement, or...