legionnaire's disease or legionnaires' disease noun

A severe, sometimes fatal, pneumonia-like disease caused by the bacterium Legionella pneumophilia (so named after an outbreak of the disease at an American Legion convention in Philadelphia in 1976)

Legion of Honour noun

A French order instituted in 1802 by Napoleon I

American Legion

An association of US war veterans

British Legion

(in full Royal British Legion) an ex-servicemen's and -women's association

Foreign Legion

A legion composed of foreigners, esp that in the French Army organized in 1831

their name is Legion

They are too many to number (from Bible, Mark 5.9)

Thundering Legion

In Christian tradition, a body of soldiers under Marcus Aurelius, whose prayers brought down a thunderstorm and destroyed the enemy