When the bumps of the spine are visibly beneath the skin on the back. Eg, Danbooru post #5470255. Often seen in cases of extreme thinness. Not to be confused with a simple line to indicate the spine eg, Danbooru post #6218597. This also does not apply to character designs with a transparent body and a visible skeleton beneath it or character designs with spines on the outside/sticking through the skin eg, Danbooru post #6844681 Danbooru post #6982123. This tag applies specifically to individual bumps visible underneath non-transparent skin.

See also:

ribs
skinny
emaciated

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