Jihad: a struggle or fight against the enemies of Islam
Generation Jihad is a reference to a group of people who are very often brainwashed with Al Qaeda propaganda, mostly through the internet.
From the Glossary:
Jihad = striving; ‘effort’ or ‘struggle’. Muslims distinguish between two forms of jihad: the inner jihad, referring to the struggle against temptation and to improve one’s own character and to a militant struggle waged to defend the (land of) Islam.