Final answer:
The technique to define the perimeter hairline, such as the nape, is known as outlining. This creates a clean hairline, differentiating it from texturizing, overcombing, and expansion tapering, which are other hair cutting methods.
Step-by-step explanation:
The cutting technique used to define the perimeter hairline, such as the nape, is known as outlining. This technique is essential in creating clean and precise edges around the hairline, making the hairstyle look polished and well-defined. In contrast, texturizing is used to add movement and texture to the hair, overcombing involves lifting the hair at a higher angle for a layered cut, and expansion tapering refers to a technique for creating shape within the haircut, often used to build weight or create a silhouette.
In reference to the law associated with visual perception in psychology, the answer to the question about choppy or jagged lines is not related to hair cutting techniques. Within the realms of Gestalt psychology, principles such as closure, good continuation, proximity, and similarity pertain to the way humans perceive and organize visual stimuli, not to hair cutting methods.