To fish bowl is to smoke marijuana in an enclosed area (like a car, closet, etc) such that the enclosed area fills with smoke and the atmosphere in the room becomes filled with enough smoke to get high from.

This is, perhaps, an "East Coast" term, as everyone that I know uses it, but people that I have talked to who live in California and other "West Coast" places refer to it as the "Hot Box".

What distinguishes this term from "hot box" however is its usage. While "fish bowl" and "hot box" both can be used as nouns to refer to the place where the smoking activity is going on, fish bowl is used almost exclusivly as a verb!

As an example, "hot box" seems to be used mostly as a noun as in:

"Dude! You put your cat in the hot box? That's just wrong man"

However, "fish bowl" is more normally used as such:

"Hey man, let's go fish bowl the closet"

It should be noted that smoking pot is quite implicit in the use of the term. However, it is occasionally used to describe similar situations with other drugs, like tobacco. However this usage is most always used as a humerous way of observing that the windows are closed or the ventilation is otherwise very bad in an area. ex:

"Man, roll a window down, there is no need to fish bowl the car"