A Josser is someone who was not born into a circus family, nor married into a circus family, but is in a circus nonetheless. The term is also used (rarely) to refer to a clergyman (Australia), or even more generally, a fool or a simpleton (Britain).
Circus jossers are not rare, but few remain in circus for any long period of time. It is very seldom that a Josser is seen in the upper hierarchy of a professional circus, their status is usually seen as lesser than that of someone of circus descent. This is due to the aforementioned dedication issue. Jossers are at a disadvantage in modern circus, because generally speaking they have not been raised in a circus discipline, or trained to the extent of their circus-born coworkers. Amateur acts (e.g. amateur clowns) are not considered Jossers unless they have worked in larger scale circus.
Such words as joss house, joss flower, and joss stick all refer to Chinese religious traditions.