D defs.my
Entry 2 senses Webster, 1913

Ornithology

/ôrˌ-nĭth-äl'-əj-ē/ · Or·ni·thol·o·gy · IPA /ˌɔɹnɪˈθɑlədʒi/
01 n. That branch of Zoology which treats of the natural history of birds and their classification.
  1. 1.
    That branch of Zoology which treats of the natural history of birds and their classification.
  2. 2.
    A treatise or book on this science.