Other forms: gunmen
A gunman is an armed man, usually a criminal one. The word news reports use before anything else is known.
It is deliberately neutral about motive, which is why it appears in the first hours of a story when nobody yet knows whether the person is a robber, a terrorist or somebody in crisis. The plural is gunmen and there is no accepted equivalent for a woman, which occasionally forces reporters into awkward wording. Shooter is the American term and is now heard in British reporting too.
1noungunmanA man armed with a gun, especially a criminal.
“A lone gunman was reported to be inside the building.”
Middle English
gunne
English
gun
English, today
gunman
From gun + -man. gun comes from Middle English gunne. From Middle English gunne,gonne, possibly from Gunnhild, a female given name formerly used as a nickname for engines of war (compare Nordic Gunn, a female name meaning “battle”). The name is composed of the Norse elements gunnr and hildr, both meaning "battle".
Etymology from Wiktionary, CC BY-SA