Greeting an OAP roughly, a youngster may be showing it

Wiktionary Word definitions in Wiktionary
n. A disconnect between members of one generation and members of the next based on the later generation developing habits, attitudes, and preferences inconsistent with the experience of the former.

Wikipedia Word definitions in Wikipedia
Generation Gap is an interactive sitcom used to teach children (ages 8–13) how to resolve conflicts amongst their peers. It first aired on PBS in 2004 as an educational television special. The unique interactive format worked in two ways: The studio audience ...

Longman Dictionary of Contemporary English Word definitions in Longman Dictionary of Contemporary English
noun EXAMPLES FROM CORPUS ▪ He tells me that they had a discussion in school about the generation gap . ▪ It seemed that he had a foot planted firmly on both sides of the generation gap . ▪ The generation gap here was too wide. ▪ The generation gap is another ...