Dictionary
de•fea•sance
Pronunciation: (di-fē'zuns), [key]—
n. Law.
1. a rendering null and void.
2. a condition on the performance of which a deed or other instrument is defeated or rendered void.
3. a collateral deed or other writing embodying such a condition.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.