Sorry about the confusion - I must admit I thought that
sprog was wider known than presumably it is. It means "child".
For future reference, have a look at
http://www.peevish.co.uk/slang/ where a lot of slang is defined. Unfortunately despite being British through and through, a lot of the expressions on there are totally unknown to me, so I wouldn't use it as an English primer.
Incidentally, the word
furiner threw me for a moment...
Following on from this query though, exactly how many pax leave the plane (in a hurry or otherwise) without parts of their anatomy?