rectus

n. any straight muscle (Anatomy)

The rectus abdominis muscle (commonly known as "abs") is a paired muscle running vertically on each side of the anterior wall of the human abdomen (and in some other animals). There are two parallel muscles, separated by a band of connective tissue called the linea alba (white line). It extends from the pubic symphysis inferiorly to the xiphisternum and lower costal cartilages superiorly.
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Noun
1. any of various straight muscles
(hypernym) muscle, musculus

n. rectus, any straight muscle (Anatomy)

(n.)
A straight muscle; as, the recti of the eye.