noun
rectus abdominis muscle
Anatomical term for the paired muscle running vertically on each side of the anterior abdominal wall, commonly referred to as the 'abs'.
腹直筋は、いわゆる「腹筋」の主要な筋肉です。
The rectus abdominis muscle is the main muscle of the so-called 'abs'.
腹筋 is the common term for abdominal muscles in general or sit-ups, while 腹直筋 specifically refers to the rectus abdominis muscle in anatomy.
Compound of 腹 (abdomen), 直 (straight), and 筋 (muscle), reflecting its straight vertical orientation.