What is "palimpsested"

Usage examples of "palimpsested".

I mean the heart pleasure you get from looking at speckled leaves or the palimpsested bark of plane trees in Provence.

I thought how odd it was that each page, no matter how flawlessly white, no matter what its inscription or watermark, always harboured another text, another identity, beneath its surface, palimpsested and invisible, like a secret ink that can be seen only when rubbed with magic dust or exposed to flame.