thumbnail sketch
1. A small picture that presents a smaller version of a larger image or proposed image. Before fully redesigning the layout of the office, the interior designer provided me with a thumbnail sketch of his initial plans.
2. A short description or preview. Class, each of you will need to submit a thumbnail sketch of your essay topic for my approval.
a thumbnail sketch
a brief or small picture or description. The manager gave a thumbnail sketch of her plans. The student wrote a thumbnail sketch of his project.