Green’s Dictionary of Slang

(US campus) a sorority.

2005		Urban Dict. 12 May 🌐 Delta Zeta has a reputation for being a northern srat, but they also can be pretty slutty.
2016		C. Eble (ed.) UNC-CH Campus Sl. Spring 2016 9: SRAT — sorority + fraternity sorority: ‘Jamie can’t come to dinner with us because she’s got some mixer at her srat’.