The Collaborative International Dictionary of English v.0.48:
Bluebottle \Blue"bot`tle\, blue-bottle \blue-bottle\, n.
1. (Bot.) an annual Eurasian plant (Centaurea cyanus) which
grows in grain fields; -- called also bachelor's button.
It receives its name from its blue bottle-shaped flowers.
Varieties cultivated in North America have showy heads of
blue or purple or pink or white flowers
Syn: cornflower, bachelor's button.
[1913 Webster + WordNet 1.5]
2. (Zool.) A large and troublesome species of blowfly (Musca
vomitoria). Its body is steel blue.