to read a book / to study, euphemism used by gamblers to replace 讀書 since書 (book) is homonymous with the word輸 (lose), which is unlucky for gamblers [colloquial]
Definitions (粵典–words.hk)
動詞
即讀書。廣東話中「書」「輸」同音，賭仔為咗避諱而改稱做讀勝 (literally: to read win) to read books; to study （a euphemism used by gamblers because 書 syū "book" is homonymous with 輸 syū "lose"）.