an adolescent prostitute who does not engage in sex with patron but allows them to touch their body
Definitions (粵典–words.hk)
名詞、舊式
喺魚蛋檔做嘢，提供色情服務（但係唔包上牀）嘅女仔（量詞：個） a girl who works at a "fishball stall", (in the past) a place offering sexual services short of sexual intercourse
Definitions (Wiktionary)
noun, Hong-Kong, dated
underaged female prostitute who works at a “fishball stall”