The Scarecrow, from the Wizard of Oz
, captured the friendly and helpful nature of disambiguation: "...some people prefer to go.....BOTH ways!"
To disambiguate is to make something less ambiguous.
Often two concepts will share a common name. On a wiki, in such a case we often make a wiki page that links to more specific pages, which aids a reader in navigation.
For instance, we have a disambiguation page for xyz. This page gives the reader an easy way to find xyz-a or xyz-b, which both have pages on our wiki.
A related concept is a redirect.