Clop is a slang term for fan-made pornography or erotic art based on the animated children's television series My Little Pony: Friendship is Magic and can be viewed either as a subset of brony fandom, furry fandom, or both.
The word itself is a pun or wordplay based on the slang word "fap", meaning "masturbation". The word is also used as a verb, to refer to the act of masturbating to clop. Other related terms include "clop-fic" for erotic fiction/slash fiction centered around My Little Pony characters, and "clopper" for a person who enjoys this type of material.
My Little Pony-inspired erotic fan art reportedly first began appearing on the web around 2012. The topic has received ample scholarly attention. To some in the fandom, "clopping" (masturbating to clop) is frowned upon. On the other hand, in 2015, the Guardian reported that in the Brony community on 4chan, having sex with a real person was seen as a negative, and not clopping as a form of heresy.
A survey from the porn site PornHub revealed that users from Russia and Ukraine were particularly over-represented when it came to perusing search terms relating to My Little Pony on said website. The Ukrainian ransomware known as "cl0p" was likely named after this phenomenon.