- incapable of being defended, as an argument, thesis, etc.; indefensible.
- not fit to be occupied, as an apartment, house, etc.
- (of theories, propositions, etc) incapable of being maintained, defended, or vindicated
- unable to be maintained against attack
- rare (of a house, etc) unfit for occupation
adj.1640s, “incapable of being held against attack,” from un- (1) “not” + past participle of tenable. Figurative sense is recorded from 1690s.