n. One of two persons jointly exercising the same office in Republican Rome.
the GNU version of the Collaborative International Dictionary of English
n. One of two Roman officers or magistrates united in the same public functions.
The Century Dictionary and Cyclopedia
n. In Roman history, one of two officers or magistrates united in the same public function.
Word Usage
"They stayed in the comfortable coolness of the house of the chief ethnarch, though these days he was a Roman citizen, and pretended he was more at ease being called a duumvir than an ethnarch."