SSR

Short definition from Wiktionary

Noun

1. 1
   Initialism of Soviet Socialist Republic.
2. 2
   Initialism of secondary surveillance radar.
3. 3
   Initialism of solid-state relay.
4. 4
   Initialism of subsurface radar, a radar picket submarine.
5. 5
   Initialism of special service requirement or special service request.
6. 6
   Initialism of sum of squared residuals.
7. 7
   Initialism of server-side rendering.
8. 8
   Initialism of sustained silent reading.
9. 9
   Initialism of small ships register.
10. 10
    Initialism of special support and reconnaissance.