The Collaborative International Dictionary of English v.0.48:

Rasure \Ra"sure\ (r[=a]"zh[-u]r; 135), n. [L. rasura, fr.
   radere, rasum, to scrape, to shave. See Rase, v.]
   1. The act of rasing, scraping, or erasing; erasure;
      obliteration.
      [1913 Webster]

   2. A mark by which a letter, word, or any part of a writing
      or print, is erased, effaced, or obliterated; an erasure.
      --Ayliffe.
      [1913 Webster]

Bouvier's Law Dictionary, Revised 6th Ed (1856):

RASURE. The scratching or scraping a writing, so as to prevent some part of
it from being read. The word writing here is intended to include printing.
Vide Addition; Erasure and Interlineation. Also 8 Vin. Ab. 169; 13 Vin. Ab.
37; Bac. Ab. Evidence, F.; 4 Com. Dig. 294; 7 Id. 202.