Unburned carbon (smoke) from a steam or diesel locomotive, or multiple unit.
Bits of rubber which are shed from tires during a race and collect off the racing line, especially on the outside of corners (cf. marbles).
A glue or paste made from starch.
Low cloud, fog or smog.
To stick, like boots in mud
Any fuel derived from hydrocarbon deposits such as coal, petroleum, natural gas and, to some extent, peat; these fuels are non-renewable, and their burning moves carbon from underground into the atmosphere via the greenhouse gas carbon dioxide.