Formless, unformed, shapeless are comparable when they mean having no definite or recognizable form.
Something is formless which is so fluid or so shifting in its outlines, structure, or character that it does not assume, or is incapable of assuming, a fixed or determinate form.
Something is unformed which has existence but has not yet attained the form or character proper to it when it has reached the height of its possible growth or development. Often it suggests crudeness or callousness.
Something is shapeless which lacks or has lost the clearcut outline or contour that is regarded as proper to a thing or essential to its beauty.