Non-Muslim opinions

Barbary Pirates
The Barbary Pirates is what Europe and the United States called the 18th century Jihad by Ottoman corsairs, an Islamic group that attacked as far north in Europe as Iceland.

Modern Views
The United States Department of Justice has used its own ad hoc definitions of jihad in indictments of individuals involved in terrorist activities:
"As used in this First Superseding Indictment, 'Jihad' is the Arabic word meaning 'holy war'. In this context, jihad refers to the use of violence, including paramilitary action against persons, governments deemed to be enemies of the fundamentalist version of Islam."
"As used in this Superseding Indictment, 'violent jihad' or 'jihad' include planning, preparing for, and engaging in, acts of physical violence, including murder, maiming, kidnapping, and hostage-taking." in the indictment against several individuals including José Padilla.
Karen Armstrong in her book "Muhammed", writes:
"Fighting and warfare might sometimes be necessary, but it was only a minor part of the whole jihad or struggle."
The Orientalist, Maxime Rodinson, wrote that "Jihad is a propagandistic device which, as need be, resorts to armed struggle – two ingredients common to many ideological movements." (Maxime Rodinson. Muhammad. Random House, Inc., New York, 2002. p. 351.)
The neologism jihadist is sometimes used to describe militant Islamic groups, including but not restricted to Jihadist terrorism.