Etymology: conjunction of the prefix "sis" (as in sister) + the Middle English "triste" - appointed station for hunters (probably from trist, trust confidence, trust)
Date: 21st century
1: an agreement to meet for an intimate affair, as made by two or more women who are unusually close, but who are not involved romantically
2: an appointed meeting or meeting place for heterosexual females to have a "date" ("date," in this instance, meaning an occasion to get dressed up and go out with the same level of exuberance as if it were a romantic date with an attractive man)
I'm totally looking forward to my sistryst on Friday night. I've bought a new outfit to wear to cocktails and dinner with the girls.