An emeritus is a retired college professor or minister. When a professor stops teaching, she might be given the title of emeritus, which basically means she can still be remembered as a successful professor.
The word emeritus, pronounced "eh-MER-ih-tus," is Latin, originally meaning "veteran soldier." The honorary adjective is most often used with professor, but it applies to other professions whose retirees continue to hold their title, like ministers. The word emeritus usually goes after the job title, but it can also come before, like emeritus editor.