adj. not liable to being annulled or declared void.
the GNU version of the Collaborative International Dictionary of English
adj. Not to be defeated; not defeasible; incapable of being annulled or made void.
The Century Dictionary and Cyclopedia
Not defeasible; not to be defeated or made void; that cannot be set aside or overcome.
WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
adj. not liable to being annulled or voided or undone
Word Usage
"If seisin corporeal, user immemorial, and prescription for levance and couchance conferred any title indefeasible, then were the rabbits the owners in fee-simple, absolute, paramount, and source of pedigree."