Bahman is right, the definition of the soul as “the form of the body” is very Catholic. The concept of hylomorphism goes back to Aristotle (see, e.g.,
De Anima ii, 2 and
iii, 4), but the Church has baptized the idea, St. Thomas and others having used it to explain certain points of theology (see, e.g.,
S.T. I, Q. 76). It doesn’t generally concern us rank-and-file faithful in our day-to-day lives, which is why we don’t hear about it from the pulpit.
Still, it is relevant today, in part because there’s a widespread notion that a man *is *his soul, and that the body is just a shell. But clearly this is not true, as the body is an integral part of a human being. Our souls are not angels; they are made to work through bodies. And we do not become angels in heaven, either (though we will be like them in respect to immortality–Lk. 20:36); our bodies are resurrected and reunited with our souls forever.
Getting back to the OP, Bahman, you wrote, “the soul is formless after death”; I think you meant to say, “the soul is without matter after death” (the body being the matter). This is indeed somewhat of a problem in metaphysics, but it is not a problem for God. The following is my own opinion. After death, God sustains the soul by a miraculous intervention, so that we can perceive, understand, and experience reality even apart from our bodies.