Senior

From Scienowiki

In Scientology, this means the person or position in an org that someone reports to, his immediate boss, as in "The senior of the D of P is the Tech Sec". The equivalent word in common usage outside of Scientology is "supervisor" (which in Scientology means course supervisor).

This does not get confused with "senior" roughly meaning "person aged over 65". The word is just not used much in this sense in an org.