pecs

from WordNet (r) 3.0 (2006)

pecs
    n 1: either of two large muscles of the chest [syn: {pectoral},
         {pectoral muscle}, {pectoralis}, {musculus pectoralis},
         {pecs}]

from The Collaborative International Dictionary of English v.0.48

pecs \pecs\ (p[e^]ks), n. pl. (Anat.) [contraction from pectoral
   muscles.]
   The pectoral muscles; -- a contraction used by body-building
   and health enthusiasts. Used similarly to {abs} and {delts}.
   [informal]
   [PJC]