Wiktionary
a. (context idiomatic English) Completely naked.
Usage examples of "buck naked".
Pithy couldn't go because he was buck naked, so he took the poker for the stove.
I've noticed that our hosts sleep buck naked and pile their clothes high on a shelf or something.
Which was as polite a way as he could manage of saying that I probably didn't want to report in officially while I was buck naked.
And then, in place of imagination, she saw a boy of twelve or so, dark of skin with tight-curled hair, shoot up out of the river not three rods off, water falling off him, shining in the sunlight, his mouth open and laughing, and in midair he sees her, and she can see his face change and in that instance she knows what he feels: embarrassment to be seen buck naked by a woman, the fading remnants of his boisterous fun, and, just dawning under the surface where his own mind couldn't know it yet, love.