Lit. 'an agreement'. During the 11c and the 12c, the barons of England and France/Normandy were almost continuously in dispute. These were private wars of the kind William I had forbidden in England after 1066 but which were not so susceptible to one authority across the Channel. The Church also sought to limit these eruptions, e.g. the *Truce of God. However, these quarrels did not always spill over into violence; likely enough, one of the two sides simply wished to agitate and secure an agreement - conventio -which might favour him slightly.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.