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).
"Let me hit that bowl, son." or "You wanna hit this bowl Kiran?" "Fuck yeah I do, Hannah, you bowl-toting mother fucker."