the part of a marijuana (weed, pot, ganja, etc.) pipe in which the marijuana is placed (packed) to be smoked. it may have a little hole (carb) on the side of it, which you cover while you are inhaling the marijuana smoke while holding the whole pipe and smoking.

bowl (n): the indentation in a pipe (generally a marijuana pipe) in which the marijuana itself is placed

Very simple device, used to hold unstable food.

The part of a device for smoking marijuana that hold the weed itself.
The pipe itself is NOT called a bowl. That is a common mistake; stop making it. Call it a pipe or a glass piece, but don't call the whole device a bowl around anyone who knows anything if you don't want to look stupid.

Bowl is the name for a pipe that weed is smoked out of. While it is technically the term used for the area in which the weed is packed, it is a term experienced potheads use for the whole pipe, because pipes are generally associated with flavored tobacco and grandfathers. If you're trying to impress a pothead with your extensive knowledge of smoking vocabulary, you should therefore use this term, or the widely-used term piece (also associated more with weed than tobacco).

Can also be used to describe .5 grams of marijuana, just enough to fit into the bowl of a pipe.

something to smoke marijuana out of. also see a pipe