In France, pétard means joint; of the cannabis variety. The
word's origins lie in the fact that "pétard" means "firecracker"
or some kind of rocket, so there are two similarities: the
shape, and the fact that all of these "pétards" have to be lit.
Oh, and they're all fun too. If you're feeling especially lazy,
you can simply say "pet". There seems to be no verlan
(backslang) equivalent of this word.