The vinculum is the processing device at the core of every Borg vessel, which brings order to chaos. It interconnects the minds of all the drones; it purges individual thoughts and disseminates information relevant to the Collective.
In 2375, Voyager encountered a malfunctioning Borg vinculum in a debris field. The vinculum tried to established a link to Seven of Nine's cortical implant, in an effort to re-integrate Seven into the Borg Collective.
Vinculum is also a latin word, meaning "a means of binding".