adj. & n.
adj. 1 of or relating to the breast or chest; thoracic (pectoral fin; pectoral muscle). 2 worn on the chest (pectoral cross).
n. 1 (esp. in pl.) a pectoral muscle. 2 a pectoral fin. 3 an ornamental breastplate esp. of a Jewish high priest.
[ ME f. OF f. L pectorale (n.), pectoralis (adj.) f. pectus pectoris breast, chest ]