A Link Condom is a slang term used to describe the protection of certain hyperlinks from being crawled and indexed by Google. These hyperlinks are “sheathed” in the NoFollow link attribute (rel=nofollow) which is used to communicate to Google’s crawler bots that the target web page of the link should not be considered.
NoFollow links are often used for internal links to protect certain webpages from indexing. They’re also used to dissociate a website from another website when one website links its content but does not wish for that link to describe a relationship between the two websites, for ranking purposes.