Definition of: chalaza

(kə·lā′zə) noun plural ·zas or ·zae (-zē)
1. Biol. One of the two spirally twisted albuminous threads that are attached to each end of the lining membrane of an egg and keep the yolk in position with the germinating spot uppermost. See illustration under EGG.
2. Bot. The part of an ovule where the coats are united to each other and to the nucellus. [<NL <Gk., hailstone, small lump]