There are a variety of synonyms for the term "backless sandal". Some options include "slider", "slip-on sandal", "mule", and "thong sandal". "Slider" refers to a sandal that slides on and off the foot, while "slip-on sandal" describes a type of footwear that is easy to put on. "Mule" describes a backless shoe with a closed toe, while "thong sandal" denotes a sandal with a strap that goes between the toes. These synonyms are useful for those seeking a specific type of sandal for comfort or fashion purposes.