The Collaborative International Dictionary of English v.0.48:

Specialism \Spe"cial*ism\, n.
   Devotion to a particular and restricted part or branch of
   knowledge, art, or science; as, medical specialism.
   [1913 Webster]

WordNet (r) 3.0 (2006):

specialism
    n 1: the concentration of your efforts on a particular field of
         study or occupation
    2: the special line of work you have adopted as your career;
       "his specialization is gastroenterology" [syn:
       specialization, specialisation, specialty,
       speciality, specialism]