The hole in the side of a marijuana pipe's bowl. More commonly known as the carb hole. After smoke has built up in the piece a smoker removes her thumb from the choke to take the hit.
1. You've got a good hit built up in the chamber, take your thumb off the choke!
2. When I want to res-rip a piece, I suck the flame through the choke hole, and use the bowl as the choke.