A tactic employed by some websites where they try and gather as many inbound links as possible while having as few outbound links as possible.

This is done to increase traffic and link popularity towards these few websites the outbound links are pointing to or to keep from passing traffic and link equity to anyone else (by marking the outgoing links as nofollow).

It is considered a disreputable tactic and it can hurt just as much as having too many outgoing links.