"Defensibility" is a word in ENGLISH

Capable of being hailed; admitting of bail; authorizing or requiring bail. A bailable action is one in which the defendant …

Capable of being defended; defensible.

Capable of being defended; as, a defensible city, or a defensible cause.

Capability of being defended; defensibility.

Capable of being defended, or of making or affording defense.

Not defensible; not capable of being defended, maintained, vindicated, or justified; unjustifiable; untenable; as, an indefensible fortress, position, cause, etc.

Capable of being held, naintained, or defended, as against an assailant or objector, or againts attempts to take or process; …

Having sufficient strength or force; founded in truth; capable of being justified, defended, or supported; not weak or defective; sound; …