adj. Capable of being defeated, terminated, annulled, voided or invalidated.
the GNU version of the Collaborative International Dictionary of English
adj. Capable of being annulled or made void.
The Century Dictionary and Cyclopedia
That may be abrogated or annulled.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. capable of being annulled or voided or terminated
Word Usage
"Besides being fallible, it seems that a priori justification is defeasible, that is, all-things-considered a priori justification can be defeated by further evidence."