The abdominal muscle that creates the 'six-pack' appearance is technically called the what?

The abdominal muscle that creates the “six-pack” appearance is technically called the rectus abdominis.

The rectus abdominis is a paired, flat skeletal muscle running vertically along the front of the abdomen. It extends from the pubic region toward the xiphoid process and the costal cartilages of the fifth through seventh ribs. Its main action is flexing the lumbar spine, as in the upward phase of a curl-up.

The muscle’s segmented appearance comes from bands of connective tissue called tendinous intersections. These divisions, together with the separate left and right sides divided by the linea alba, create the familiar blocks associated with a “six-pack.” The visible definition depends not only on muscle development but also on genetics, body-fat distribution, and lighting.

The rectus abdominis is different from the transverse abdominis, which wraps horizontally around the trunk, and the obliques, which run along the sides. Exercises such as crunches can strengthen the rectus abdominis, but no single exercise can selectively remove fat from the abdomen. The informal term “abs” may refer to the whole abdominal region, while the anatomical answer is more precise.