adj. 25B6; adjective
a defensible attitude : JUSTIFIABLE, arguable, tenable, defendable, supportable; plausible, sound, sensible, reasonable, rational, logical; acceptable, valid, legitimate; excusable, pardonable, understandable.
a defensible territory : SECURE, safe, fortified; invulnerable, impregnable, impenetrable, unassailable.
untenable, vulnerable.