It's a valid question.
A slush pile is the mountain of poorly written, vain-hope query letters doing a bad job of expressing the author's meagerly fulfilled plot concept that agents and publishers must "slush" through to find, in the words of Agent Ziva from NCIS, "the needle in the needle stack."
I do like that analogy. Imagine a stack of rusty, bent needles, and you're trying to find that one that is, ideally, straight and clean (though you'd settle for mostly straight and a small enough amount of rust that a good bit of CLR could set it right). The entire endeavor sounds painful, both literally and figuratively.
So, I'm a slush pile hero. I've sent my novel out into the pile, and fought through enough to be noticed. No offers yet, but maybe one's coming soon. If not, at least I haven't let the slush pile beat me down.
Sometimes, that's all you can ask for.