Cosignitary

Pronunciation: k?-s?g"n?-t?-r?
a.

1. Signing some important public document with another or with others; as, a treaty violated by one of the cosignitary powers.
   

n. pl. Cosignitaries (-rz).

1. One who signs a treaty or public document along with others or another; as, the cosignitaries of the treaty of Berlin.