What does defeasibly mean?
'Defeasibly' is an adverb describing something held or established in a way that can be undone. Rooted in law, it applies to interests, titles, or rights that are valid only until a specified condition occurs or a superior claim emerges: an estate conveyed defeasibly may revert to its grantor if a stated contingency arises. Beyond the courtroom, philosophers of logic and knowledge use the term to describe conclusions that are warranted yet revisable — beliefs that stand unless defeated by new evidence. The word derives from the Old French 'defaire', meaning to undo or destroy, entering English through Anglo-Norman legal usage alongside 'defeasible' and 'defeasance'. Because it signals built-in fragility beneath apparent finality, 'defeasibly' is valuable wherever precision about conditional validity matters: contracts, wills, statutes, and epistemological argument alike.
In a manner subject to annulment or termination upon the occurrence of a specified condition or event.
"The trustees held the fund defeasibly, with title passing outright only if the beneficiary completed university."
Chiefly used in legal drafting concerning property interests and estates.
In a manner such that a conclusion or justification holds only in the absence of defeating counterevidence.
"Perception provides reasons that are only defeasibly conclusive, since illusions can undermine them."
A right held defeasibly looks absolute — until the one condition hidden inside it comes due.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of defeasibly
'Defeasibly' is formed from the adjective 'defeasible', which entered English legal vocabulary in the early modern period via Anglo-Norman French, ultimately from Old French 'defaire' ('to undo, undo, destroy'), from Late Latin 'disfacere' ('to undo'). The same Latin root underlies English words such as 'defeat' and, more distantly through different Romance development, 'feasible' and 'feat'. The adverb retains its strongest home in property law, where 'defeasible' describes estates capable of being terminated.
Related word forms
How defeasibly is actually used
Predominantly a technical legal term, appearing almost exclusively in property law and formal academic writing on logic and epistemology. It carries a dry, precise register and would sound out of place in ordinary conversation.
Easily confused with defeasibly
'Feasibly' means 'in a way that can be done or achieved', while 'defeasibly' means 'in a way that can be annulled or overturned'.