Any of various South American hummingbirds with a sharp pointed bill

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Thornbill \Thorn"bill`\, n. (Zo["o]l.) Any one of several species of small, brilliantly colored American birds of the genus Rhamphomicron . They have a long, slender, sharp bill, and feed upon honey, insects, and the juice of the sugar cane.

WordNet Word definitions in WordNet
n. any of various South American hummingbirds with a sharp pointed bill

Wiktionary Word definitions in Wiktionary
n. Any of the passerine birds of the genus ''Acanthiza''.