A CORDIS was the Word Lord equivalent of a TARDIS. CORDIS stood for Conveyance Of Repeating Dialogue In Space-time. (AUDIO: The Word Lord) CORDISes were described by the seventh Doctor as a complex linquistic structure and a non physical TARDIS.
CORDISes ran on common words and phrases used throughout the multiverse and disguised themselves as such. The CORDIS chameleon circuit was called a chameleon meme by the Seventh Doctor. These disguises could be jokes, expressions, or any other kind of phrase. (AUDIO: A Death in the Family)
While in these disguises the CORDIS's chameleon meme would be unable to hide the pulse of its engines, which would be the repetition of those phrases which would be repeated periodically.
A CORDIS was able to translate matter in a manner that allowed their operator to assume a physical appearance that allowed them to interact with members from N space, and provide them with whatever they needed. The CORDIS Nobody No-One used provided him with a number of weapons while giving him a physical form that made him virtually indestructible.