indefensible vs untenable

indefensible and untenable both are adjectives.

Word	Noun	Adjective	Verb	Adverb
indefensible	No	Yes	No	No
untenable	No	Yes	No	No

As adjectives, indefensible and untenable are synonyms defined as:

indefensible and untenable: (of theories etc) incapable of being defended or justified

indefensible (adjective)	untenable (adjective)
incapable of being justified or explained	(of theories etc) incapable of being defended or justified
(of theories etc) incapable of being defended or justified
not able to be protected against attack