backlink

Short definition from Wiktionary

Noun

1. 1
   A hyperlink to a webpage from an external website.
2. 2
   A reference to an object on another server, allowing it to be updated periodically.
3. 3
   A link to another page that links to the current one, often in an automatically assembled list of links to all other such pages, allowing for bidirectional navigation.

Verb

1. 1
   To link in this fashion.