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. 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.