Other forms: dottles
Use the noun dottle to describe the leftover, unburnt tobacco that's left in a pipe after it's been smoked. Your grandfather might knock the dottle from his pipe into the kitchen trash can every afternoon.
Dottle is a very old-fashioned word that's specific to a fairly old-fashioned activity, pipe smoking. A well-packed pipe is meant to burn all the tobacco in its bowl, but sometimes there's a damp wad of smelly dottle left behind. The word, which is rarely used these days, was originally dossil, from the French word dosil, "a spigot or plug in a vessel." It became a pipe-smoking term in the early nineteenth century.