sacred ibis Syllabification: (sa·cred i·bis)Definition of sacred ibis noun a mainly white ibis with a bare black head and neck and black plumes over the lower back, native to Africa and the Middle East, and venerated by the ancient Egyptians. Threskiornis aethiopicus, family Threskiornithidae sacred ibis in other Oxford dictionaries Definition of sacred ibis in the British & World English dictionary