1.  ss(n = noun.group) secret service, united states secret service, us secret service, usss - the United States intelligence agency that protects current and former presidents and vice presidents and their immediate families and protects distinguished foreign visitors; detects and apprehends counterfeiters; suppresses forgery of government securities and documents;
is a kind of united states intelligence agency
is a part of department of homeland security, homeland security

2.  ss(n = noun.group) schutzstaffel - special police force in Nazi Germany founded as a personal bodyguard for Adolf Hitler in 1925; the SS administered the concentration camps;
is a kind of constabulary, law, police, police force
has parts: gestapo

ss, abbr.
1 Saints.
2 steamship.
3 hist. Nazi special police force.

Etymology:
sense 3 f. G Schutz-Staffel