—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
Useful english dictionary. 2012.