sicklebill Syllabification: (sick·le·bill)Pronunciation: /ˈsikəlˌbil/Definition of sicklebill noun any of a number of birds with a long narrow down-curved bill. a tropical American hummingbird (genus Eutoxeres, family Trochilidae: two species). a New Guinea bird of paradise (two genera in the family Paradisaeidae). sicklebill in other Oxford dictionaries Definition of sicklebill in the British & World English dictionary