An established(ie: long used) term referring to WW2 vets, however, it was self given(I think..) and is generally used in one of two ways...
1)arrogantly, often something along the lines of the first definition for this word(^)
2)by pacifists who wish to not seem that way or who wish to not be thought of as ungrateful
"Hey! We're the Greatest Generation you hippie punks!"
"What sacrifices, they truely are the greatest generation..."
The generation of men and women who selflessly served in the armed forces of America during WW2 and helped stop the tide of Nazi and Japanese aggression. Alot better than today's generation of pacifist pussies and terrorist appeasers. With the exception of those in the armed forces now. God Bless them.
The Greatest Generation is sadly fading away, day by day. The memorial dedicated to their service to their country will be the most beautiful this country ever built.