An expression designed to call somthing to mind without mentioning it explicity; an indirect or passing reference.

Allusion- An expression used to call something to mind without directly mentioning it.

Example from the text-

“I was only on the outside” (Piggy, line 19, page 194). Piggy is trying to tell Ralph he is innocent for the death of Simon. He doesn’t directly say “I didn’t do it”, but rather I was there, but I had no involvement.

Allusion: a passing or casual reference; an incidental mention of something, either directly or by implication: an allusion to Shakespeare.