In the following question, out of the four alternatives, select the alternative which best expresses the meaning of the idiom/phrase.
An outline representing or bounding the shape or form of something.

Let's look at the definitions of the given words:
contour: An outline representing or bounding the shape or form of something.

tracery: Ornamental stone openwork, typically in the upper part of a Gothic window.

doodle: A rough drawing made absentmindedly.

pattern: A repeated decorative design.

Therefore, contour is the most accurate definition for the phrase.