In humans and some other mammals, the soleus is a powerful muscle in the back part of the lower leg (the calf). It runs from just below the knee to the heel, and is involved in standing and walking. It is closely connected to the gastrocnemius muscle and some anatomists consider them to be a single muscle, the triceps surae. Its name is derived from the solefish whose shape it resembles.
See more at Wikipedia.org...
So·le·us n. A muscle with origin from the head and shaft of the fibula, the medial margin of the tibia, and the tendinous arch passing between the [more]Soleus - Community and Resources
Noun 1. a broad flat muscle in the calf of the leg under the gastrocnemius muscle (synonym) soleus muscle (hypernym) skeletal muscle, striated muscle (part-holonym) calf, sura