desert-neon answered:

For the original ask, requesting the definition of squick, please see this post.

Squick is a fun term that was often used as both a noun and a verb. Either X was one of your squicks, or X squicked you, or squicked you out, or squicked you hard.

It was often used in fic exchanges. They would ask for a list of your squicks so that the gifting author would know not to include any hint of them. It was also used in casual conversation with fandom friends, authors, artists, etc. It could be left in comments, or as a reason you just didn’t read your best fandom friend’s latest fic. “Sorry, bff, you know I love your writing, but you have X tagged at the top, and that just squicks me out.” “Hey, no worries, best reader friend! I totally get it. Give this one a pass, but I’ll send you a note when I post my next one! I promise it will be totally X-free!”

Here’s the thing though. In your example, you explain why X is your squick with Y. But the beauty of squick was that (at least in my experience) no explanation was necessary. Not only was it not necessary, it was rarely asked for. A squick is a squick, and there doesn’t have to be any rhyme or reason. In fact, why would you have a rational, bullet-pointed, well-thought-out argument as to why something squicked you out? Very often it’s a visceral reaction, and if you don’t like the thing, you’re likely not going to sit and do deep meditation on why not.

Squicks were respected by fandom. You don’t like the thing, okay, we will tag the thing appropriately, you do not have to read the thing, no judgments on either side. There was no fandom policing, only respect.

And this, I think, is super important, because fandom policing is a problem, especially when it comes to triggers. “Trigger” has become so overused, so all-encompassing, that people feel they have to defend their legitimate triggers. If X triggers you, it triggers you, and you DO NOT need to provide an explanation. But because “trigger” is so often used in place of “squick,” some people feel they have the right to “call out” those who use the word. They want explanations, they want you to tell them what that triggering concept does to you, so they can call bullshit and feel superior. You don’t have to explain either your squicks or your triggers, but using the correct word stops the fandom police from feeling as though they have the right to ask.

Bring “squick” back, people. Don’t devalue triggers, which are horrible, nasty, dangerous things.