An allusion is a reference to some event or person having a striking resemblance to the subject under discussion. Thus the sentence 'Drivers who drink keep Charon working overtime' refers to a figure in Greek mythology whose duty it was to ferry the dead across the River Styx into Hades. … A reporter watching a favored being upset by a weak one may suggest the effect on the spectators by saying 'The crowd couldn't have been more shocked if the Christian had started to eat the lion.'
An allusion provides a flash of wit or insight but if the reader does not recognize the allusion it will mean nothing and leave the meaning obscure. For this reason one should always be reasonably sure that the allusions will be familiar to the audience they are being written for.
