Final answer:
An aponeurosis is a wide, thin, sheetlike tendon that serves as an attachment point for convergent muscles, such as the pectoralis major and the latissimus dorsi muscles.
Step-by-step explanation:
A wide, thin, sheetlike tendon is known as an aponeurosis. This structure is a flat, broad tendon that serves as an attachment point for convergent muscles, which spread across a large area and converge at a common point. An example of such a convergent muscle is the pectoralis major, which attaches to the greater tubercle of the humerus. Similarly, the latissimus dorsi muscles in the lower back attach to a broad sheet of connective tissue called an aponeurosis.