Royal Navy slang for something
useless. It took me ages to work this one out.
Obviously, if you're wearing a
motorcycle helmet it would be
kinda difficult to smoke.
Frater 219 points out that, in addition, the ashes would fly out. Great, thanks. It's only taken me FIVE YEARS to realise that. And I thought I had problems before... sigh.
sideways says let it be noted though, that motorcycle legend Barry Sheen used to have a hole bored in his helmet so he could have a puff on the starting line at races. so the legends go at least... ;-)
Compare chocolate teapot, waterproof teabag, solar-powered torch, and so on and so on. Or, as used by Rimmer in an episode of Red Dwarf, "you are about as much use as a condom machine in the Vatican".