Razoring is the act of slicing out sections of library materials.
For example, a law school student cuts out a page from a reference book that provides information on a court case being covered in class -- presumably to prevent other students from having access to the information. (The student could also deliberately mis-shelve or otherwise hide or steal the book for the same reasons.)
Such acts of vandalism may also be committed by those who bear some grudge against the library, wish to censor certain materials, or have some psychological disorder.
As members of a profession charged with preserving information -- a charge long challenged (cf. book burning) -- librarians are often disturbed by razoring.
With the advent of electronic forms of information, library collections are less vulnerable to razoring, although now crackers may attempt to compromise library computers and systems.