What is "koryo-mar"

Koryo-mar, Goryeomal or Koryŏmal ( Hangul: 고려말; ; Standard Korean: 중앙아시아 한국어, literally Central Asian Korean language) is the dialect of the Korean language spoken by the Koryo-saram, ethnic Koreans in the former USSR. It is descended from the Hamgyŏng dialect. Koryo-saram often report difficulty understanding speakers of standard Korean; this may be compounded by the fact that the majority of Koryo-saram today use Russian and not Korean as their native language.