what is a good definition of the "lost generation"

I always think of them as the young adults who remain in Europe after WWII and who have lost their purpose and will to succeed in life. Hence the term. I think this is the Gertrude Stein definition - can anyone verify this?

It can also be more broadly interpreted to mean the entire generation of soldiers who got killed in WWII and hence would mean that entire generation that will fail to meet its potential because of the huge loss of life and limbs (and even the survivors who are unable to restart their lives following all the trauma).

Actually, the lost generation is the generation of adults after World War I, not II. This generation was completely crushed by the mechanized tools of destruction used in WWI, such as, poison gas and strong bombs. This generation let go of all their values and instead picked up these new values of easy sex, materialism, and mental incompetence. Also the fact that Jake Barnes is injured from the war and become impotent causes much pain for him. This generation was in fact coined by Gertrude Stein. -Hope that helped.