What's an everyday use of an allusion?

An allusion is an indirect reference to an outside work. Saying something like "chocolate was her Achilles' heel" or "he was a Good Samaritan" are everyday uses of allusions - showing indirect references to Achilles and the Bible.

allusion is an indirect passing of something. so for example if your teacher asks if you did your homework and you say, "I started to do it ... " You are indirectly saying that you didn't do it.