slang for cocaine. Evolved from the slang term yay (yayo). As the term yay became more popular, a new word was needed as code for coke so one could speak openly about it in public without evesdroppers become wise to the subject of the conversation. The term shmay has since evolved even further into shmizzle, or even shmizzle shmazzle... if you are not into the whole brevity thing.
Yo, wassup with some shmay tonight?