bluebottle

Concise Oxford English Dictionary © 2008 Oxford University Press:
bluebottle/ˈbluːbɒtl/

▶noun

• 1 a common blowfly with a metallic-blue body. [Calliphora vomitoria.]

• 2 Austral. & S. African the Portuguese man-of-war.

• 3 Brit. the wild cornflower.

• 4 Brit. informal, dated a police officer.