If you thought someone had spilled paint on the wall, you may have been looking at an abstraction, or an example of abstract expressionism, or a treatment of an abstract or highly subjective motif, not an abstract.
An abstract is a summary of the main points of a complicated document, such as a deed or a will.
Abstract, as an adjective, has to do with things that are difficult to understand, such as an abstract painting by Jackson Pollock. The trick is not to hang it upside down.
