noun

• (anatomy) Any of a number of muscles controlling the movement of the eyeball.
• (anatomy) Any of several straight muscles in various parts of the body, as of the abdomen, thigh, eye etc. [(anatomy) A paired muscle running vertically on each side of the anterior wall of the abdomen in humans and some other mammals.]
• (anatomy) Ellipsis of rectus abdominis. [(anatomy) A paired muscle running vertically on each side of the anterior wall of the abdomen in humans and some other mammals.]