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.
Etymology: ME f. OF f. L pectorale (n.), pectoralis (adj.) f. pectus pectoris breast, chest