generation gap

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A difference in values and attitudes between one generation and another, especially between young people and their parents.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun 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.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a difference between the views of young people and their parents