peroneus brevis UK /pɛ.ɹə(ʊ)ˌniː.əs ˈbɹɛv.ɪs/US /ˌpɛɹ.əˌni.əs ˈbɹɛv.ɪs/ noun1 •A muscle of the lateral side of the leg that arises from the lower part of the fibula, ends in a tendon that inserts on to the fifth metatarsal bone, and acts to evert and pronate the foot. formsperonei breves