De‐fea″sance (?), n. [OF. defesance, fr. defesant, F. défaisant, p. pr. of defaire, F. défaire, to undo. See Defeat.] 1. A defeat; an overthrow.
After his foes' defeasance. Spenser.
2. A rendering null or void.
3. (Law) A condition, relating to a deed, which being performed, the deed is defeated or rendered void; or a collateral deed, made at the same time with a feoffment, or other conveyance, containing conditions, on the performance of which the estate then created may be defeated.
☞ Mortgages were usually made in this manner in former times, but the modern practice is to include the conveyance and the defeasance in the same deed.