WordNet (r) 3.0 (2006):

Selective Service
    n 1: an independent federal agency that administers compulsory
         military service [syn: Selective Service, Selective
         Service System, SSS]
    2: compulsory military service [syn: conscription, muster,
       draft, selective service]

Moby Thesaurus II by Grady Ward, 1.0:

22 Moby Thesaurus words for "selective service":
   active service, call, call-up, compulsory military service,
   conscription, draft, draft call, drafting, duty, enlistment,
   enrollment, impressment, induction, levy, mobilization, muster,
   national service, press, recruiting, recruitment, service,
   summons