The Collaborative International Dictionary of English v.0.48:

Chalaza \Cha*la"za\, n.; pl. E. Chalazas, L. Chalaz[ae].
   [NL., fr. Gr. ? hail, pimple.]
   1. (Bot.) The place on an ovule, or seed, where its outer
      coats cohere with each other and the nucleus.
      [1913 Webster]

   2. (Biol.) A spiral band of thickened albuminous substance
      which exists in the white of the bird's egg, and serves to
      maintain the yolk in its position; the treadle.
      [1913 Webster]