The main idea of being called Eldritch Abomination is
There are no words that can encompass such disgusting foulness, not in English or any other human tongue. They are The Other. The Inconceivable. Alien beyond comprehension, their sole existence is an affront to all reason.
So the answer to your question is 无 (not to be confused with µ if trying to find a link!) — the question itself must be “unasked”; no answer can exist in the terms provided.
Use of the Eldritch Abomination in storytelling requires that no details be given. The reader/viewer/player has inherent fear of the unknown or brings up fears from his own imagination that works specifically for him.
Jaws (movie version) turned out much better because they couldn’t get the robot shark to work and Stephen directed it instead to not show it. Remember the scene with the roast and the dock? Or Brody on the beach just waiting for the monster to appear? Showing only the protagonist, that was scary.
So what makes the scene so good? In the first episode of new video essay series “The Discarded Image,” Julian Palmer suggests the answer is Spielberg’s knack for putting the audience in the place of the actor: The director uses color choice, camera placement, and foreshadowing to go “beyond the proscenium arch” and engage viewers directly. He’s not the first to do so, of course, and Palmer frequently uses Alfred Hitchcock’s work to contextualize Spielberg’s innovations in suspense.
(Bold mine) That is, the nature of the monster is not at all important here, is never shown and not yet present, and the fear (in the story as well as in the viewing) comes from the inner fears of the protagonist.
Likewise, the first Alien movie was much scarier before the alien was seen in detail, and the fragments that showed were, well, alien, so you didn't know how it fit together from seeing the parts. Once it became known in diagrams and cultural references, it culminated in the Far Side cartoon of “Alien family dinners” and was definitely not scary anymore.
I've never liked horror films before, because in the end it's always been a man in a rubber suit. Well, there's one way to deal with that. The most important thing in a film of this type is not what you see, but the effect of what you think you saw. —Ridley Scott
As for Lovecraft’s squid, not everyone finds them scary or creepy. Invertebrates might have been creepy to New England fisherman, and he likes to use cool words like squamous, but today finding a live Architeuthis is really cool, not horrifying.
(Fine art is not smut…it's acceptable as a featured image on Wikipedia, right? But under spoiler tag just in case.)
So no, not even Google can help. “What is it?” is what it is. You have to find it within yourself to bring forth the worst fears you can imagine, and fear the unknown.