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| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
breastbone breast·bone (brěst'bōn')
n.
See sternum.
| breastbone (brěst'bōn') Pronunciation Key
See sternum. |
breastbone
in the anatomy of tetrapods (four-limbed vertebrates), elongated bone in the centre of the chest that articulates with and provides support for the clavicles (collarbones) of the shoulder girdle and for the ribs. Its origin in evolution is unclear. A sternum appears in certain salamanders; it is present in most other tetrapods but lacking in legless lizards, snakes, and turtles (in which the shell provides needed support). In birds an enlarged keel develops, to which flight muscles are attached; the sternum of the bat is also keeled as an adaptation for flight
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