in the altogether vs in the buff

in the altogether and in the buff both are adjectives.

Word	Noun	Adjective	Verb	Adverb
in the altogether	No	Yes	No	No
in the buff	No	Yes	No	No

As adjectives, in the altogether and in the buff are synonyms defined as:

in the altogether and in the buff: (used informally) completely unclothed

Other synonyms of in the altogether include bare-ass, bare-assed, in the raw, naked as a jaybird, peeled, raw, stark naked.

in the altogether (adjective)	in the buff (adjective)
(used informally) completely unclothed	(used informally) completely unclothed