a broad marketing term often describing different things, but in general links deemed to be harmful for search engine rankings in Google and other search engines at varying grades.

Toxic Links are

Links with high risk to cause a Google penalty (manual action) or (partial) ranking demotion (rankings drop) to your website.

That’s a whole mouthful, isn’t it? Toxic links sounds easier, right?

Toxic Links are backlinks that are understood as a high risk to hurt your organic rankings.

Toxic links could possibly harm the search engine rankings of a website.

Toxic Links is a term that became popular among SEOs to describe what it does, intoxicate your backlink profile - i.e. increase the risk for a Google Penalty.

Background context:

When Google introduced negative effects of links officially in 2012 with the Google Penguin Updates, it became apparent that the more overweight of negative affecting links you have in your backlink profile - the worse.

Unofficially such toxic links were known almost a decade longer.

Google has always issued (silent) penalties or demotions for specific “silver bullet links” (we believe that term was coined by ©Dave Naylor 2007).

Now instead of toxic links many people also can use any of the following terms and they may be more or less precise.