"The Eldritch Abomination is a type of creature defined by its disregard for the natural laws of the universe as we understand them. They are grotesque mockeries of reality beyond comprehension whose disturbing otherness cannot be encompassed in any mortal tongue."-Tv tropes
Eldritch Abominations are in essence incomprehensible beings whose very nature defy the natural laws of reality and then some. An example being Nylarathotep from the Cthulu Mythos, and Cthulu himself.