In cycle racing, a (notional) honour held (by analogy with the
maillot jaune for the leader) by the rider lying last on
general classification in a
stage race, or by extension the holder of that position.
In major races like the Tour de France, a certain degree of fame - and hence enhanced start money in other races - is attached to this position, such that riders have been known to compete quite vigorously for it; this is a tricky game to play since riders who fail to finish within a time limit based on a percentage of the winner's time in any given stage are eliminated.
In the Giro d'Italia the equivalent title is the maglia nera; a black jersey was actually awarded for a few years in the postwar era - doubling as a mocking gesture to the blackshirts of the fascist era.