The true defininition: a cause, principle, or system of beliefs held to with faith.
Essentially: yes, those people who are religious have caused death, but this is not due to the religion itself. Imagine how many lives have been saved by religion! The reality is that religion is the principle by which all institutions are created Without it, we wouldn't be where we are today.
hospitals, peace treaties, schools...just to name a few
Albert Einstein, Abraham Lincoln, Ghandi, Thomas Jefferson, Darwin(!), Winston Churchill, Ronald Reagan, Kennedy, Mother Teresa, Martin Luther King Jr.
--would you rather live in a world without religion? ...I certainly don't want to.