소의 is a name of rank given for royal concubine(후궁). And it is the forth position in the ranking. Here is a list of rank: 왕비(王妃) 빈(嬪) 귀인(貴人) 소의(昭儀) 숙의(淑儀) 소용(昭容) 숙용(淑容) 소원(昭媛) 숙원(淑媛)