palimpsest

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A manuscript, typically of papyrus or parchment, that has been written on more than once, with the earlier writing incompletely scraped off or erased and often legible.
• noun An object or area that has extensive evidence of or layers showing activity or use.

from The Century Dictionary.

• noun A parchment or other writing-material from which one writing has been erased or rubbed out to make room for another; hence, the new writing or manuscript upon such a parchment.
• noun Any inscribed slat, etc., particularly a monumental brass, which has been turned and engraved with new inscriptions and devices on the reverse side.

from the GNU version of the Collaborative International Dictionary of English.

• noun A parchment which has been written upon twice, the first writing having been erased to make place for the second. The erasures of ancient writings were usually carried on in monasteries, to allow the production of ecclesiastical texts, such as copies of church services and lives of the saints. The difficulty of recovering the original text varied with the process used to prepare the parchment for a fresh writing; the original texts on parchments which had been washed with lime-water and dried were easily recovered by a chemical process, but those erased by scraping the parchment and bleaching are difficult to interpret. Most of the manuscripts underlying the palimpsests that have been revived are fragmentary, but some are of great historical value. One Syriac version of the Four Gospels was discovered in 1895 in St. Catherine's Monastery at Mount Sinai by Mrs. Agnes Smith Lewis. See also the notes below.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A manuscript or document that has been erased or scraped clean, for reuse of the paper, parchment, vellum, or other medium on which it was written. Many historical texts have been recovered using ultraviolet light and other technologies to read the erased writing.
• noun archaic Monumental brasses that have been reused by engraving of the blank back side.
• noun astronomy Circular features believed to be lunar craters that have been obliterated by later volcanic activity.
• noun geology Geological features thought to be related to features or effects below the surface.
• noun computing Memory that has been erased and re-written.
• noun Something bearing the traces of an earlier, erased form.
• verb To scrape clean, as in parchment, for reuse.
• verb On paper: to reuse, often by erasure or change of pen direction or color. Especially fueled by Earth Day.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a manuscript (usually written on papyrus or parchment) on which more than one text has been written with the earlier writing incompletely erased and still visible